docs: release notes for the v21.0.5 release #2592

Job	Run time
lint	1m 55s
build	17s
build-e2e-windows	18s
test	0s
Browser Compatibility Tests	-1s
e2e-package-managers	-1s
publish-snapshots	-1s
e2e-snapshots	-1s
e2e	-1s
e2e-windows	0s
	2m 25s

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