Basic Firebase Rust wasm-bindgen bindings

[NickHu]

We will need to be able to use the Firebase JS SDK from Rust. This means either writing our own binding, or seeing if there is one that is suitable. We expect to want to use Firebase Auth, Storage, and Cloud Firestore in our client.

[NickHu]

There is a very new binding available: https://github.com/jquesada2016/firebase-wasm-rs

It requires appraisal, but might be what we are looking for, or at least a decent starting point.

[NickHu]

@thud @H-Yulong could one of you take a look at this? I wrote up the design in the README for https://github.com/orgs/homotopy-io/projects/8

[H-Yulong]

firebase-wasm-rs looks fine, I'll give it a try.