l10n: add ja_JP #210

Job	Run time
Test Python package build (macos-13)	44s
Lint & Test (macos-13)	2m 30s
Test Python package build (macos-14)	20s
CodeQL (javascript)	1m 19s
Lint & Test (macos-14)	1m 48s
Test Briefcase build (macos-13)	3m 12s
CodeQL (python)	1m 30s
Lint & Test (windows-2022)	2m 28s
Test Briefcase build (macos-14)	1m 53s
Lint & Test (ubuntu-22.04)	1m 13s
Test Briefcase build (windows-2022)	3m 10s
Test documentation build	18s
Test Python package build (windows-2022)	28s
Test Briefcase build (ubuntu-22.04)	2m 55s
Test Python package build (ubuntu-22.04)	12s
Upload coverage	2s
Deploy github pages	0s
Briefcase build & draft release	0s
Publish to PyPi	0s
	24m 2s

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