test: example app

[johannes-lindgren]

A basic example application for two purposes:

Testing

A simple test to test that:

1. package JSON exports is configured correctly
2. type declarations and the bundle is generated correctly
3. That some essential functions and types are exported from the library

If there's an issue, the dependent React application will fail to type check and build.

Documentation

As a demo to draw inspiration from. When using this library for the first time, I found the barrier to entry to be a bit higher than necessary. The idea is to demonstrate:

1. Asynchronous loading: the current example in the Readme only shows how to utilize a global state that is initialized at the time the module is loaded. However, in a real-world scenario, the application will likely connect the Yjs document to some server or local storage.
2. Non-global state: the example in the readme loads the document in the module, but a real-world application might want to be more flexible, for example by using React's context API.
3. How to handle type safety. When passing the type argument to binder<T>(), Immer-yjs essentially asserts the type. However, the user might want to validate the document to guarantee proper type safety. (I developed a validation library just for this purpose—PureParse—to deal specifically with data from CRDTs)
4. Example on how to integrate with React. The readme uses an outdated function useSyncExternalStoreWithSelector: React now has useSyncExternalStore.

[johannes-lindgren]

@sep2 I'm converting to draft, because I am working on this right now.