[WASM] Add wasm-bindgen-test to CI and add a test and instructions for how to test the wasm wrapper.

[daidoji]

1. Add wasm-bindgen-test showing how to test for the Dater implemention example.
2. Add wasm tests to CI of base repository
3. Add documentation on how to write a wasm-bindgen-test for the wrapper.

Per PR review comment #155 (comment)