tools: add workflow to review Nix changes #11

Job	Run time
x86_64-linux: Evaluate shell.nix	59s
aarch64-darwin: Evaluate shell.nix	2m 19s
x86_64-darwin: Evaluate shell.nix	3m 45s
aarch64-linux: Evaluate shell.nix	53s
compare	5s
	8m 1s

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