Add Mauritania holidays #4287

Job	Run time
Run pre-commit	20s
Test Python 3.8 on macos-latest	1m 3s
Test Python 3.9 on macos-latest	41s
Test Python 3.10 on macos-latest	39s
Test Python 3.11 on macos-latest	38s
Test Python 3.12 on macos-latest	48s
Test Python 3.8 on ubuntu-latest	58s
Test Python 3.9 on ubuntu-latest	52s
Test Python 3.10 on ubuntu-latest	50s
Test Python 3.11 on ubuntu-latest	52s
Test Python 3.12 on ubuntu-latest	1m 17s
Test Python 3.8 on windows-latest	1m 26s
Test Python 3.9 on windows-latest	1m 35s
Test Python 3.10 on windows-latest	1m 44s
Test Python 3.11 on windows-latest	1m 44s
Test Python 3.12 on windows-latest	2m 7s
Build distribution	19s
Test build on macos-latest	26s
Test build on ubuntu-latest	43s
Test build on windows-latest	1m 45s
Publish to PyPI	0s
	20m 47s

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