Add changelog for next 0.5.x release #3608

Job	Run time
document	53s
check-links	55s
smoke (amaranth-lang/amaranth-boards)	32s
test (3.8)	2m 44s
smoke (amaranth-lang/amaranth-stdio)	58s
test (3.9)	2m 44s
smoke (amaranth-lang/amaranth-soc)	1m 0s
test (3.10)	4m 7s
test (3.11)	2m 50s
test (3.12)	4m 12s
test (pypy-3.8)	9m 36s
test (pypy-3.9)	9m 2s
test (pypy-3.10)	5m 44s
test (3.13-dev)	3m 28s
publish-docs	6s
publish-docs-dev	0s
required	1s
publish-schemas	8s
publish-package	14s
publish-release	0s
	49m 14s

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