build

doc: add comment to explain the syntax of folded examples #14664

Job	Run time
build (ubuntu-latest)	4m 27s
Build jj-lib without Git support	47s
build (macos-13)	6m 27s
cargo-deny (advisories)	25s
build (macos-14)	3m 40s
Check protos	25s
build (windows-latest)	8m 27s
build (ubuntu-latest, --all-features)	5m 24s
cargo-deny (bans licenses sources)	27s
Clippy check	2m 30s
Check that MkDocs can build the docs	23s
Check that MkDocs can build the docs with Poetry 1.8	22s
Check formatting	17s
	34m 1s

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