build

github: add action to check dotslash files #13395

Job	Run time
Check protos	27s
Build jj-lib without Git support	42s
cargo-deny (advisories)	23s
build (ubuntu-latest)	4m 29s
cargo-deny (bans licenses sources)	24s
Clippy check	2m 34s
build (macos-13)	6m 53s
Check that MkDocs can build the docs	20s
build (macos-14)	3m 40s
build (windows-latest)	9m 27s
Check that MkDocs can build the docs with Poetry 1.8	24s
build (ubuntu-latest, --all-features)	5m 31s
Check formatting	15s
	35m 29s

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