Add VERSIONING.md, ROADMAP.md, and DEPENDENCY_POLICY.md #4180

Job	Run time
checks / readme-snippets	12s
checks / test (3.12, highest, windows-latest)	3m 0s
checks / test (3.13, lowest-direct, ubuntu-latest)	47s
checks / test (3.11, highest, ubuntu-latest)	46s
checks / test (3.12, lowest-direct, ubuntu-latest)	50s
checks / test (3.11, lowest-direct, windows-latest)	2m 39s
checks / test (3.10, lowest-direct, ubuntu-latest)	47s
checks / test (3.13, lowest-direct, windows-latest)	2m 23s
checks / test (3.13, highest, ubuntu-latest)	48s
checks / test (3.11, highest, windows-latest)	2m 49s
checks / test (3.13, highest, windows-latest)	2m 29s
checks / test (3.12, highest, ubuntu-latest)	1m 3s
checks / test (3.12, lowest-direct, windows-latest)	3m 11s
checks / test (3.10, lowest-direct, windows-latest)	2m 18s
checks / test (3.10, highest, ubuntu-latest)	50s
checks / test (3.10, highest, windows-latest)	2m 8s
checks / pre-commit	38s
checks / test (3.11, lowest-direct, ubuntu-latest)	43s
all-green	5s
	28m 26s

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