* Support {CD}
* Edit screenshotter test to fit on one page
* Update screenshots
* Remove bogus Safari screenshot
* Edit documentation to avoid tag conflicts and explain delimiters
* Add type annotations
* Add bogus safari screenshot
* Update with real Safari screenshot
* Set label vertical alignment
* Revise call to parseExpression() per PR 2085 changes to macro parsing
* Update Firefox screenshot
* Pick up review comments
* Add unit tests and snapshot.
* Tighten up label collection.
* Better loop index
* remove extra space
* Picked up comments. Added a parse check. Added a test.
Co-authored-by: ylemkimon <y@ylem.kim>
Co-authored-by: Kevin Barabash <kevinb@khanacademy.org>
Co-authored-by: Kevin Barabash <kevinb7@gmail.com>