Add wasm-bindgen feature to README/docs

[qdot]

Just found out there's a wasm-bindgen feature via the PR then reading the Cargo.toml. Would be nice to have this in the README.

[najamelan]

Wouldn't it be better to automatically turn these dependencies on on wasm? AFAICT the library can't work on wasm without them. It would save users from having to fiddle with feature flags.

[qdot]

Sure, that'd work too.

[dariusc93]

Wouldn't it be better to automatically turn these dependencies on on wasm? AFAICT the library can't work on wasm without them. It would save users from having to fiddle with feature flags.

I agree that it would be better to have it enabled based on the target, especially since it doesnt fail to build on non-wasm32 targets, it makes it hard to debug the time not implemented on this platform panic message when Instant or SystemTime is used from std due to Instant being used by the native module.