Consider implementing `wasm-bindgen` conversion traits for various `time` structs

[demhadais]

Hello! Just wanna start by saying I love the crate. I would like to improve the support for the structs in this crate by implementing FromWasmAbi and friends for structs in this crate, converting them to js_sys::Date. Maybe I could also implement support for converting structs in this crate to Temporal API objects behind some unstable feature flag and/or compilation options. This would enable users to do things like:

use wasm_bindgen::prelude::*;
use time::UtcDateTime;

#[wasm_bindgen]
struct MyStruct {
    pub time: UtcDateTime
}

I'd be happy to submit a PR with these changes if it sounds good!

[jhpratt]

I haven't used wasm-bindgen in a very long time; the support only exists because others wanted it. What would this enable that is not currently possible? I don't know off-hand what that snippet is supposed to do.

Regarding potential implementation, feature flags are inherently stable; it's all or nothing. Additionally, given the name of the trait and its method, does this not necessarily want me to promise a certain ABI? That's a nonstarter if so, as I reserve the right to change the ABI of any struct in any manner, and in fact did so for most structs not that long ago.