docs: release notes for the v20.3.0 release #8617

Job	Run time
build	4s
build-e2e-windows	3s
lint	4s
e2e-windows	1s
publish-snapshots	1s
Browser Compatibility Tests	1s
test	1s
e2e-package-managers	1s
e2e-snapshots	1s
e2e	1s
	18s

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