[add] CheckBox component

Implements the CheckBox component and adds a web-only 'color' prop to
allow the color of the checkbox to be customized.

docs/storybook/1-components/CheckBox/CheckBoxScreen.js

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+/* eslint-disable react/jsx-sort-props */
+
+/**
+ * @flow
+ */
+
+import CustomSize from './examples/CustomSize';
+import PropColor from './examples/PropColor';
+import PropDisabled from './examples/PropDisabled';
+import PropOnValueChange from './examples/PropOnValueChange';
+import PropValue from './examples/PropValue';
+import React from 'react';
+import UIExplorer, {
+  AppText,
+  Code,
+  Description,
+  DocItem,
+  Section,
+  storiesOf
+} from '../../ui-explorer';
+
+const CheckBoxScreen = () => (
+  <UIExplorer title="CheckBox" url="components/CheckBox">
+    <Description>
+      <AppText>
+        This is a controlled component that requires an <Code>onValueChange</Code> callback that
+        updates the value prop in order for the component to reflect user actions. If the{' '}
+        <Code>value</Code> prop is not updated, the component will continue to render the supplied{' '}
+        <Code>value</Code> prop instead of the expected result of any user actions.
+      </AppText>
+    </Description>
+
+    <Section title="Props">
+      <DocItem name="...View props" />
+
+      <DocItem
+        description="Customize the color of the checkbox."
+        example={{
+          render: () => <PropColor />
+        }}
+        label="web"
+        name="color"
+        typeInfo="?color"
+      />
+
+      <DocItem
+        description="If true, the user won't be able to interact with the checkbox."
+        example={{
+          render: () => <PropDisabled />
+        }}
+        name="disabled"
+        typeInfo="?boolean = false"
+      />
+
+      <DocItem
+        description="Invoked with the event when the value changes."
+        name="onChange"
+        typeInfo="?function"
+      />
+
+      <DocItem
+        description="Invoked with the new value when the value changes."
+        example={{
+          render: () => <PropOnValueChange />
+        }}
+        name="onValueChange"
+        typeInfo="?function"
+      />
+
+      <DocItem
+        description="The value of the checkbox. If `true` the checkbox will be checked."
+        example={{
+          render: () => <PropValue />
+        }}
+        name="value"
+        typeInfo="?boolean = false"
+      />
+    </Section>
+
+    <Section title="More examples">
+      <DocItem
+        description="The checkbox size can be controlled by the 'height' and 'width' style properties"
+        example={{
+          code: '<CheckBox style={{ height: 32, width: 32 }} />',
+          render: () => <CustomSize />
+        }}
+        name="Custom size"
+      />
+    </Section>
+  </UIExplorer>
+);
+
+storiesOf('Components', module).add('CheckBox', CheckBoxScreen);

docs/storybook/1-components/CheckBox/examples/CustomSize.js

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+/**
+ * @flow
+ */
+
+import React from 'react';
+import styles from './styles';
+import { CheckBox, View } from 'react-native';
+
+const CustomSizeExample = () => (
+  <View style={styles.row}>
+    <View style={styles.marginRight}>
+      <CheckBox style={{ height: 20, width: 20 }} value />
+    </View>
+    <View style={styles.marginRight}>
+      <CheckBox style={{ height: 32, width: 32 }} value />
+    </View>
+  </View>
+);
+
+export default CustomSizeExample;

docs/storybook/1-components/CheckBox/examples/PropColor.js

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+/**
+ * @flow
+ */
+
+import React from 'react';
+import styles from './styles';
+import { CheckBox, View } from 'react-native';
+
+const CheckBoxColorExample = () => (
+  <View style={styles.row}>
+    <View style={styles.marginRight}>
+      <CheckBox color="#1DA1F2" value />
+    </View>
+    <View style={styles.marginRight}>
+      <CheckBox color="#F45D22" value />
+    </View>
+  </View>
+);
+
+export default CheckBoxColorExample;

docs/storybook/1-components/CheckBox/examples/PropDisabled.js

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+/**
+ * @flow
+ */
+
+import React from 'react';
+import styles from './styles';
+import { CheckBox, View } from 'react-native';
+
+const CheckBoxDisabledExample = () => (
+  <View style={styles.row}>
+    <View style={styles.marginRight}>
+      <CheckBox disabled value={false} />
+    </View>
+    <View style={styles.marginRight}>
+      <CheckBox disabled value />
+    </View>
+  </View>
+);
+
+export default CheckBoxDisabledExample;

docs/storybook/1-components/CheckBox/examples/PropOnValueChange.js

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+/**
+ * @flow
+ */
+
+import styles from './styles';
+import React, { PureComponent } from 'react';
+import { CheckBox, Text, View } from 'react-native';
+
+class CheckBoxOnValueChangeExample extends PureComponent {
+  state = {
+    eventSwitchIsOn: false,
+    eventSwitchRegressionIsOn: true
+  };
+
+  render() {
+    const { eventSwitchIsOn, eventSwitchRegressionIsOn } = this.state;
+
+    return (
+      <View style={styles.row}>
+        <View style={[styles.alignCenter, styles.marginRight]}>
+          <CheckBox
+            onValueChange={this._handleEventSwitch}
+            style={styles.marginBottom}
+            value={eventSwitchIsOn}
+          />
+          <CheckBox
+            onValueChange={this._handleEventSwitch}
+            style={styles.marginBottom}
+            value={eventSwitchIsOn}
+          />
+          <Text>{eventSwitchIsOn ? 'On' : 'Off'}</Text>
+        </View>
+        <View style={styles.alignCenter}>
+          <CheckBox
+            onValueChange={this._handleEventSwitchRegression}
+            style={styles.marginBottom}
+            value={eventSwitchRegressionIsOn}
+          />
+          <CheckBox
+            onValueChange={this._handleEventSwitchRegression}
+            style={styles.marginBottom}
+            value={eventSwitchRegressionIsOn}
+          />
+          <Text>{eventSwitchRegressionIsOn ? 'On' : 'Off'}</Text>
+        </View>
+      </View>
+    );
+  }
+
+  _handleEventSwitch = value => {
+    this.setState({ eventSwitchIsOn: value });
+  };
+
+  _handleEventSwitchRegression = value => {
+    this.setState({ eventSwitchRegressionIsOn: value });
+  };
+}
+
+export default CheckBoxOnValueChangeExample;

docs/storybook/1-components/CheckBox/examples/PropValue.js

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+/**
+ * @flow
+ */
+
+import React from 'react';
+import styles from './styles';
+import { CheckBox, View } from 'react-native';
+
+const CheckBoxValueExample = () => (
+  <View style={styles.row}>
+    <View style={styles.marginRight}>
+      <CheckBox value={false} />
+    </View>
+    <View style={styles.marginRight}>
+      <CheckBox value />
+    </View>
+  </View>
+);
+
+export default CheckBoxValueExample;

docs/storybook/1-components/CheckBox/examples/styles.js

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+/**
+ * @flow
+ */
+
+import { StyleSheet } from 'react-native';
+
+const styles = StyleSheet.create({
+  row: {
+    flexDirection: 'row',
+    flexWrap: 'wrap'
+  },
+  marginRight: {
+    marginRight: 10
+  },
+  marginBottom: {
+    marginBottom: 10
+  },
+  alignCenter: {
+    alignItems: 'center'
+  }
+});
+
+export default styles;

docs/storybook/1-components/CheckBox/helpers.js

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+/**
+ * @flow
+ */
+
+import React from 'react';
+import { StyleSheet, View } from 'react-native';
+
+const DividerHorizontal = () => <View style={styles.horizontalDivider} />;
+const DividerVertical = () => <View style={styles.verticalDivider} />;
+
+export const styles = StyleSheet.create({
+  horizontalDivider: {
+    width: '0.6rem'
+  },
+  verticalDivider: {
+    height: '1.3125rem'
+  },
+  row: {
+    flexDirection: 'row',
+    flexWrap: 'wrap'
+  },
+  marginRight: {
+    marginRight: 10
+  },
+  marginBottom: {
+    marginBottom: 10
+  },
+  marginVertical: {
+    marginVertical: 5
+  },
+  alignCenter: {
+    alignItems: 'center'
+  }
+});
+
+export { DividerHorizontal, DividerVertical };