Add `huak-toolchain` (first-pass) #432

Job	Run time
Clippy lints	37s
Build and test (ubuntu-latest)	59s
Build with maturin	2m 17s
Formatting check	17s
Build and test (windows-latest)	1m 0s
Build and test (macos-latest)	1m 5s
	6m 15s

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