Add utils for WebGPU support detection & Instance creation

[Wumpf]

Connections

• Fixes webgl fallback fails in some browsers. #6166

Description
Targeting both WebGPU & WebGL at the same time works but is a pain right now. These new utilities and doc lines should make this a lot easier!

Would be nice to make use of this in the official examples, but don't quite know yet how - the examples on web today are geared towards explicit selection.

Testing

Testing done via https://github.com/Wumpf/minifb_wgpu_web_and_desktop/tree/better-webgpu-selection

• test on native (should no-op)
• test browser without navigator.gpu
• test browser with navigator.gpu no actual webgpu support (Chrome on Linux!)
• test on browser with webgpu support

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[Wumpf]

@rukai can you check if this solves the problem for you? I don't have a good repro setup for it right now
Either by using the new new_instance_with_webgpu_detection method yourself or by checking with running cargo xtask run-wasm on https://github.com/Wumpf/minifb_wgpu_web_and_desktop/tree/better-webgpu-selection
Thank you!