Add Guernsey holidays #5185

Job	Run time
Run pre-commit	27s
CodeQL	1m 33s
Test Python 3.9 on macos-latest	50s
Test Python 3.10 on macos-latest	55s
Test Python 3.11 on macos-latest	1m 4s
Test Python 3.12 on macos-latest	1m 20s
Test Python 3.13 on macos-latest	58s
Test Python 3.9 on ubuntu-latest	1m 4s
Test Python 3.10 on ubuntu-latest	1m 5s
Test Python 3.11 on ubuntu-latest	56s
Test Python 3.12 on ubuntu-latest	1m 32s
Test Python 3.13 on ubuntu-latest	1m 14s
Test Python 3.9 on windows-latest	1m 54s
Test Python 3.10 on windows-latest	1m 53s
Test Python 3.11 on windows-latest	2m 10s
Test Python 3.12 on windows-latest	2m 17s
Test Python 3.13 on windows-latest	2m 41s
Test docs build	34s
Build distribution	27s
Test build on macos-latest	30s
Test build on ubuntu-latest	53s
Test build on windows-latest	2m 10s
Publish generated artifacts	0s
	28m 27s

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