[fix] Jest preset module export

Export the preset as a module so that paths can be resolved relative to a Jest
config file.

Close #1290

packages/react-native-web/jest-preset.js

@@ -0,0 +1,7 @@
+module.exports = {
+  moduleNameMapper: {
+    '^react-native$': require.resolve('./dist/cjs')
+  },
+  setupFiles: [require.resolve('./jest/setup.js')],
+  testEnvironment: require.resolve('jest-environment-jsdom')
+};

packages/react-native-web/jest-preset.json

@@ -1,9 +0,0 @@
-{
-  "moduleNameMapper": {
-    "^react-native$": "<rootDir>/node_modules/react-native-web/dist/cjs"
-  },
-  "setupFiles": [
-    "<rootDir>/node_modules/react-native-web/jest/setup.js"
-  ],
-  "testEnvironment": "jsdom"
-}

packages/react-native-web/package.json

@@ -11,7 +11,7 @@
   "files": [
     "dist",
     "jest",
-    "jest-preset.json",
+    "jest-preset.js",
     "src",
     "!**/__tests__"
   ],