chore: release 0.12.8 #876

Job	Run time
docs	1m 13s
doctest	1m 25s
clippy	54s
feature-checks	3m 19s
fmt	12s
test stable (ubuntu-latest)	58s
test stable --all-features (ubuntu-latest)	1m 54s
test 1.83 (ubuntu-latest)	54s
test stable (macos-latest)	1m 9s
test stable --all-features (macos-latest)	2m 50s
test 1.83 (macos-latest)	1m 4s
test stable (windows-latest)	3m 14s
test stable --all-features (windows-latest)	4m 2s
test 1.83 (windows-latest)	3m 17s
deny / cargo deny check	19s
	26m 44s

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