Rust

Add a multiline blockquote extension #608

Job	Run time
clippy_format	1m 11s
build_wasm	1m 7s
lockfile	1m 21s
build_test (nightly)	1m 40s
build_test (beta)	1m 15s
no_features_build_test (nightly)	31s
build_test (stable)	2m 28s
no_features_build_test (beta)	34s
no_features_build_test (stable)	1m 4s
build_spec (nightly)	1m 30s
build_spec (beta)	1m 30s
build_spec (stable)	1m 14s
	15m 25s

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