Bevy: FrameTimeDiagnosticsPlugin fails on WASM

[mrk-its]

Bevy version
current master branch

Operating system & version
Ubuntu 20.04

What you did
Run bevy text example with bevy_webgl2

What you expected to happen
Example runs without errors

What actually happened

panicked at 'time not implemented on this platform', library/std/src/sys/wasm/../unsupported/time.rs:39:9

[amberkowalski]

Would we want to disable the plugin on WASM or find a workaround, because this is a limitation of WASM itself.

[chemicstry]

Just replace std::time::Instant with instant crate which supports wasm and is compatible with std. I think this was already done with some other part of bevy.