docs: add ROADMAP, VERSIONING, and dependency policy for SEP-1730 compliance #4154

Job	Run time
checks / readme-snippets	14s
checks / test (3.12, lowest-direct, windows-latest)	3m 58s
checks / test (3.13, highest, windows-latest)	2m 32s
checks / test (3.11, lowest-direct, windows-latest)	2m 42s
checks / test (3.12, highest, windows-latest)	3m 25s
checks / test (3.11, highest, ubuntu-latest)	49s
checks / test (3.13, lowest-direct, windows-latest)	2m 25s
checks / test (3.10, highest, ubuntu-latest)	54s
checks / test (3.13, highest, ubuntu-latest)	45s
checks / test (3.13, lowest-direct, ubuntu-latest)	45s
checks / test (3.12, highest, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, ubuntu-latest)	45s
checks / test (3.10, lowest-direct, windows-latest)	3m 50s
checks / pre-commit	18s
checks / test (3.12, lowest-direct, ubuntu-latest)	53s
checks / test (3.10, highest, windows-latest)	3m 10s
checks / test (3.11, highest, windows-latest)	2m 35s
checks / test (3.10, lowest-direct, ubuntu-latest)	49s
all-green	4s
	31m 48s

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