WASM Support

[elliotsayes]

Trying to build for web gives:
don't know how to build Lua for wasm32-unknown-unknown
..originating from the lua-src-rs package. That package does support wasm, but only the wasm32-unknown-emscripten target which doesn't work with bevy

[makspll]

As you see this is likely not possible until both mlua and bevy support a common wasm target