docs: add docs for backends, features, and examples #38

Job	Run time
windows-crate-v0.60.0	53s
windows-crate-v0.59.0	1m 8s
windows-crate-v0.61.3	2m 17s
linux-armv7	1m 4s
windows-x86	1m 46s
macos	1m 11s
ios	2m 29s
android	1m 42s
linux-x64	24s
wasm-wasm32-unknown-emscripten---release	47s
wasm-wasm32-unknown-unknown---features=audioworklet	51s
wasm-wasm32-wasip1-	18s
wasm-wasm32-unknown-unknown---features=wasm-bindgen	35s
windows-x64	4m 10s
linux-arm64	25s
publish	0s
	20m 0s

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