style: add rustfmt.toml with edition 2021 #26

Job	Run time
linux-arm64	29s
linux-x64	18s
windows-crate-v0.61.3	2m 11s
windows-crate-v0.59.0	59s
windows-crate-v0.60.0	54s
ios	2m 3s
macos	1m 8s
windows-x86	1m 37s
linux-armv7	1m 11s
windows-x64	1m 35s
wasm-wasm32-unknown-unknown---features=audioworklet	53s
wasm-wasm32-wasip1-	14s
wasm-wasm32-unknown-emscripten---release	53s
wasm-wasm32-unknown-unknown---features=wasm-bindgen	37s
android	1m 31s
publish	0s
	16m 33s

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