Add public repository guidance and copyright headers #29

Job	Run time
sdist	16s
linux (ubuntu-24.04-arm, aarch64-unknown-linux-gnu)	5m 13s
macos (x86_64-apple-darwin)	2m 20s
windows (x86_64-pc-windows-msvc)	6m 20s
macos (aarch64-apple-darwin)	3m 24s
linux (ubuntu-latest, x86_64-unknown-linux-gnu)	3m 45s
Smoke (local) windows-latest py3.12	44s
Publish to PyPI	-1s
Smoke (registry) ${{ matrix.os }} py${{ matrix.python }}	0s
Report registry smoke failure	0s
	22m 1s

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