GitLab

Give an example of a trivial grammar. Tweak some wording. Add some internal
links.

Bug: None
Change-Id: I28e5fd06906f347dde558fe08b02221ba075189a
Reviewed-on: https://chromium-review.googlesource.com/c/1437896
Commit-Queue: Chris Palmer <palmer@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626304}