wasm web-sys support

[emilk]

Hi, and thanks for this useful library!

What would make it even more useful to me is if worked on the web (wasm32-unknown-unknown), probably using window.performance.memory.usedJSHeapSize.

[emilk]

Blocked on rustwasm/wasm-bindgen#3159

[Arc-blroth]

WASM support also sounds useful to me, so feel free to shoot a PR when that gets unblocked!

(sorry for the late response I've been busy with college)

[emilk]

This is now unblocked:

https://docs.rs/web-sys/latest/web_sys/struct.Performance.html#method.measure_user_agent_specific_memory

Note that it is chrome-only, and behind the web_sys_unstable_apis feature flag.

Anways, I don't have time to work on this right now, but I'm leaving this here for someone else, or for future me :)

[Arc-blroth]

I'm slightly hesitant to include this API in memory-stats right now, since it is both unstable and vendor-specific; that being said at least #8 should unblock building on WASM right now