Bump version to 2.8.0 #683

Job	Run time
ci-data	4s
Compile native gem for x64-mingw-ucrt	1m 47s
Compile native gem for arm64-darwin	1m 44s
Compile native gem for aarch64-linux	1m 43s
Compile native gem for x86_64-linux-musl	1m 46s
Compile native gem for aarch64-linux-musl	1m 45s
Compile native gem for x86_64-darwin	1m 55s
Compile native gem for x86_64-linux	4m 53s
	15m 37s

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