build

wip: implement `jj docs` command #9728

Job	Run time
Check protos	30s
cargo-deny (advisories)	22s
build (ubuntu-latest)	3m 28s
Clippy check	2m 34s
cargo-deny (bans licenses sources)	22s
build (macos-14)	2m 41s
Check that MkDocs can build the docs	24s
Check that MkDocs can build the docs with Poetry 1.3.2	36s
build (windows-latest)	7m 34s
Check formatting	15s
build (ubuntu-latest, --all-features)	4m 21s
	23m 7s

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