l10n: add ja_JP #209

Job	Run time
Test documentation build	13s
CodeQL (javascript)	1m 17s
CodeQL (python)	1m 20s
Lint & Test (macos-13)	2m 5s
Lint & Test (macos-14)	1m 49s
Test Briefcase build (macos-13)	2m 18s
Test Python package build (macos-13)	32s
Lint & Test (windows-2022)	2m 2s
Test Python package build (macos-14)	32s
Test Briefcase build (macos-14)	2m 7s
Lint & Test (ubuntu-22.04)	1m 12s
Test Briefcase build (windows-2022)	4m 46s
Test Python package build (windows-2022)	37s
Test Python package build (ubuntu-22.04)	13s
Test Briefcase build (ubuntu-22.04)	39s
Upload coverage	3s
Deploy github pages	0s
Briefcase build & draft release	0s
Publish to PyPi	0s
	21m 45s

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