HmacSha256::new_from_slice(&js_string_secret.as_bytes()) =>
 HmacSha256::new_from_slice(js_string_secret.as_bytes())

 No need to pass in address here.

 Same for js_string_message.

Also drop javy_ prefix in anticipation of switching to winter cg.

Ran `cargo fmt -- --check`, and applied suggestions, per ci feedback.

No clear reason on why it fails

Replace read/write message field with update field to match nodejs
crypto api.

Add tests for failure conditions.

Clean up string error handling in digest method.

- addess lint warnings
- renamed variables for clarity
- improved method names for clarity
- clarified fn definition comments

Partial implementation, including:
- crypto.subtle.sign method
- setup wpt testing infra

Missing:
- validation of sign protocol (hmac and sha256)
- add verify method
- return value promise to match API format

This commit improves the `crypto` feature handling by making the
relationship between crypto and the experimental_event_loop explicit. If
`crypto` is defined, the `experimental_event_loop` feature will also be
enbabled.

Additionally, this commit makes it easier to define the async crypto
APIs by introducing a `crypto.js` file that defines JS bits to make it
easier to return a promise.

This allows the crypto tests to run