Add some file types to `pygments.dropdown-choices`.

Summary: I could just add these options to my local configuration, but I figured I'd submit these upstream since they are (in my opinion) fairly common file formats.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9319