This adds filamentjs to libs, which builds a Filament-only WASM file.
Unlike our existing web demos, this WASM file contains no application
code.
These bindings are by no means complete, but they are sufficient for a
"hello triangle" demo that I have working locally. Sneak peak of the
Triangle JS app code:
https://gist.github.com/prideout/e9d6dd0e312146c8a287d2d109affa4d
This commit merely adds the bindings to the build. Demos and docs are
forthcoming.