docs: introduce about webpack and metro bundler (#2434)

# Summary
Short explanation on how to configure the webpack bundler and a brief
rationale on why it's preferable to use the Metro bundler.

## Checklist
- [x] I added documentation in `README.md`

USAGE.md

@@ -145,6 +145,40 @@ export default () => {
   );
 };
 ```
+# Web configuration
+
+## Metro bundler
+No additional steps are required when using Metro bundler.
+
+## Webpack
+If you are using the Webpack bundler, the following steps are needed:
+
+- Install `@react-native/assets-registry/registry` as a project dependency.
+- Ensure that you have the proper configuration to parse flow files from `@react-native/assets-registry/registry`.
+- Configure the Webpack `module -> rules` section and include an important rule for `node_modules/@react-native/assets-registry/registry`.
+
+webpack.config.js
+ ```ts
+ const babelLoaderConfiguration = {
+  include: [
+    path.resolve(
+      appDirectory,
+      // Important!
+      'node_modules/@react-native/assets-registry/registry',
+    ),
+  ],
+  ...
+};
+
+module.exports = {
+  ...config,
+  module: {
+      rules: [babelLoaderConfiguration],
+    },
+};
+ ```
+
+For more details on the complete Webpack configuration, you can refer to this [documentation](https://necolas.github.io/react-native-web/docs/multi-platform/#compiling-and-bundling) on how to set up a `webpack.config` file for React Native Web.
 
 # Use with svg files