Tests

Respect gitignore (#169) #1124

Job	Run time
cargo-mutants	1h 17m 26s
incremental-mutants	0s
build (macOS-latest, stable)	2m 24s
build (macOS-latest, nightly)	3m 8s
build (macOS-latest, 1.70)	3m 4s
build (ubuntu-latest, stable)	1m 29s
build (ubuntu-latest, nightly)	1m 26s
build (ubuntu-latest, 1.70)	1m 49s
build (windows-latest, stable)	2m 50s
build (windows-latest, nightly)	2m 46s
build (windows-latest, 1.70)	3m 2s
	1h 39m 24s

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