Use WebPack to build and serve the Web version of the example

[JoseLion]

In the example app, we support React Native Web using the Metro bundler with the metro.config.web.js configuration to create a bundled JS file to consume it from the index.html. This is not ideal for two reasons:

1. We are only creating a bundle that can be used directly at production, so we don't have a way to handle everything related to web development (assets, code splitting, CSS/styling, etc.).
2. We don't have a real development server, we just use a static server to serve the bundled JS on the index.html

Known issues

The main reason we started with a static server was that the example project is a workspace on a mono repo, so we need to find a way to consume react-native-spotlight-tour from another workspace and be able to replace all references to react-native imports with react-native-web. For iOS and Android, we use rnx-kit to solve this problem. But the web structure is different and rnx-kit doesn't seem to work as expected.