Promote the v2 README to README.md ahead of the first v2 beta #3182

Job	Run time
checks / docs	42s
checks / readme-snippets	11s
checks / pre-commit	49s
checks / test (3.11, locked, windows-latest)	1m 59s
checks / test (3.10, lowest-direct, windows-latest)	1m 52s
checks / test (3.13, locked, ubuntu-latest)	1m 10s
checks / test (3.10, locked, ubuntu-latest)	1m 11s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.11, lowest-direct, windows-latest)	1m 50s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.13, locked, windows-latest)	1m 59s
checks / test (3.10, locked, windows-latest)	1m 50s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 16s
checks / test (3.12, locked, windows-latest)	1m 50s
checks / test (3.12, lowest-direct, windows-latest)	1m 48s
checks / test (3.13, lowest-direct, windows-latest)	1m 52s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.11, locked, ubuntu-latest)	1m 19s
checks / test (3.12, locked, ubuntu-latest)	1m 24s
checks / test (3.14, lowest-direct, windows-latest)	1m 56s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 30s
checks / test (3.14, locked, ubuntu-latest)	2m 15s
checks / test (3.14, locked, windows-latest)	2m 28s
all-green	4s
	34m 55s

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