Rust

Expand traverse and descendants documentation: Issue #369 #663

Job	Run time
build_wasm	41s
clippy_format	1m 12s
lockfile	59s
build_test (nightly)	1m 12s
build_test (beta)	1m 12s
no_features_build_test (nightly)	28s
build_test (stable)	1m 12s
no_features_build_test (beta)	33s
no_features_build_test (stable)	32s
build_spec (nightly)	1m 13s
build_spec (beta)	1m 1s
build_spec (stable)	1m 11s
	11m 26s

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