Implement `wasm_bindgen` conversion traits for `Uuid`

[demhadais]

Hi! I read #653, and I was wondering if I could submit a simple PR implementing the conversion traits (like FromWasmAbi and friends) that just treats a Uuid to a string (converting it to and from Rust with Uuid's FromStr and Display impls). I think this is reasonable given that the JavaScript standard library produces v4 UUIDs as strings by default.

If this makes sense, I'd love to submit a PR with these trait implementations!

[KodrAus]

Thanks for pointing that out @demhadais. That's certainly a point in favor of representing UUIDs as strings, but still isn't a single obviously correct representation for all possible users. I would be in favor of implementing the traits on our formatting adapters like Hyphenated that represented them as strings as a starting point.

[demhadais]

@KodrAus I see - that makes sense to me. I'll get started on a PR, though you should note that the wasm-bindgen module in which these traits reside is explicitly marked as "unstable". Specifically, "no stability guarantees are provided". I thought this wasn't an issue, but the maintainer of jiff (a datetime crate) brought up good points in BurntSushi/jiff#424 because I wanted to submit a similar PR for the types in that crate. To summarize, even minor version upgrades might present breaking changes, which could pose a problem for uuid. I'm not sure how much of a problem that's actually going to be; taking a cursory glance at the history of this module, I don't see much actual change - it's mostly documentation stuff and non-breaking changes.

In any case, I did submit wasm-bindgen/wasm-bindgen#4256, but if you'd prefer to wait for a response to that issue and see if there are stronger semver-compatibility guarantees, that would also make sense to me.

Thanks!

[KodrAus]

Ah yes, without wasm-bindgen being stable we’d need to add this behind a feature flag and using a compiler variable the same way we do for zerocopy. If you did want to take a crack at this I can give you some pointers on how that works.