Prepare 20.0.0 release. #1399

Job	Run time
mypy	34s
ruff	7s
sdist	1m 6s
parse_sdl (macos-latest, 3.2.16)	28s
parse_sdl (windows-latest, 3.2.16)	53s
test-docs	1m 57s
pyodide	3m 14s
tox (ubuntu-latest)	2m 8s
build-macos (cp314t-*_universal2)	2m 13s
build-macos (pp310-*)	3m 58s
build-macos (cp310-*_universal2)	2m 23s
linux-wheels (aarch64, cp314t-manylinux*)	4m 29s
linux-wheels (aarch64, cp310-manylinux*)	4m 12s
linux-wheels (x86_64, pp310-manylinux*)	4m 0s
linux-wheels (aarch64, pp310-manylinux*)	3m 35s
linux-wheels (x86_64, cp310-manylinux*)	4m 11s
build (windows-latest, 3.14t, x64)	3m 23s
build (windows-latest, pypy-3.10, x64)	3m 41s
build (windows-latest, 3.10, x64)	3m 37s
build (ubuntu-latest, pypy-3.10, x64)	3m 24s
build (ubuntu-latest, 3.10, x64)	3m 34s
build (ubuntu-latest, 3.14t, x64)	3m 40s
linux-wheels (x86_64, cp314t-manylinux*)	4m 12s
build (windows-11-arm, 3.11, arm64)	4m 49s
build (windows-11-arm, 3.14t, arm64)	5m 12s
build (windows-latest, 3.10, x86)	3m 47s
build (windows-latest, 3.14t, x86)	4m 34s
publish	57s
	1h 24m 18s

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