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Add pre-commit and zizmor configuration. #345

Job	Run time
config	16s
Pre-commit checks / Pre-commit Checks	13s
build (iOS)	7m 35s
build (visionOS)	4m 29s
build (tvOS)	7m 58s
build (watchOS)	7m 47s
build (macOS)	59s
Briefcase testbed (iOS)	5m 0s
CPython testbed (visionOS)	4m 1s
Briefcase testbed (macOS)	2m 7s
CPython testbed (iOS)	2m 22s
Cross-platform env test (arm64-iphonesimulator)	40s
Cross-platform env test (x86_64-iphonesimulator)	47s
CPython testbed (tvOS)	3m 29s
Cross-platform env test (arm64-iphoneos)	34s
	48m 17s