Update changelog for v0.5.5 #3708

Job	Run time
smoke (amaranth-lang/amaranth-boards)	32s
smoke (amaranth-lang/amaranth-soc)	56s
smoke (amaranth-lang/amaranth-stdio)	1m 1s
check-links	47s
document	50s
test (3.9)	3m 16s
test (3.13)	3m 0s
test (3.10)	2m 20s
test (3.11)	2m 48s
test (pypy-3.9)	6m 53s
test (3.12)	4m 27s
test (pypy-3.10)	4m 34s
test (3.14-dev)	34s
publish-docs	6s
publish-docs-dev	0s
required	2s
publish-package	11s
publish-schemas	5s
publish-release	0s
	32m 22s

Provide feedback