Port to JavaScript

This release ports the internals of Replicache from Rust to pure JavaScript.

This release reduces the replicache package size by over 83% (brotli compressed, Replicache is now just 32kb) and improves performance on most of our benchmarks.

However, this is just the beginning because there are many further opportunities being in JS opens up to both improve performance and further reduce package size.

In the below images, the red line is the last Rust commit.