docs/changes: Add RFC 66 changes. #3558

Job	Run time
check-links	50s
test (3.8)	2m 38s
document	46s
test (3.9)	2m 37s
smoke (amaranth-lang/amaranth-boards)	39s
test (3.10)	3m 50s
smoke (amaranth-lang/amaranth-stdio)	41s
test (3.11)	3m 21s
smoke (amaranth-lang/amaranth-soc)	45s
test (3.12)	3m 45s
test (pypy-3.8)	5m 23s
test (pypy-3.9)	5m 43s
test (pypy-3.10)	4m 59s
test (3.13-dev)	3m 10s
publish-docs	14s
publish-docs-dev	0s
required	1s
publish-package	48s
publish-schemas	14s
publish-release	0s
	40m 24s

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