mls-rs WASM wrapper

Note that Safari WebDriver needs to be enabled manually for wasm-pack to work.

``shell
sudo safaridriver --enable
`

Build and test using headless Chrome

`shell
just test
`

Dependencies

- rustup
- rust-toolchain.toml pins a specific version of Rust, which will be picked up by rustup,
- node:
- .nvmrc pins a specific version of Node, which will be picked up by nvm,
- wasm-pack:
- brew install wasm-pack, or
- cargo install wasm-pack, or
- there is also NPM version which is slightly slower,
- yarn,
- wasm-opt (optional):
- brew install binaryen,
- just (optional):
- brew install just`.