Test WASM/JS on CI

[sffc]

The GitHub Actions CI currently only runs make in example/c and example/cpp. We should really be testing the WASM/JS on CI as well. Related: there are no instructions I can find explaining how to rebuild the example.wasm file and run the demo locally.

[sffc]

For anyone else who is wondering: here is how I was able to run the WASM example:

1. At the top level, run cargo build --target wasm32-unknown-unknown
2. At the top level, start an HTTP server with a command such as python3 -m http.server
3. In your browser, navigate to http://localhost:8000/example/js/
4. Open the JS console to view the output