Summary: This is kind of a quick hack to make symbol lookup work for C#. ctags calls C# 'csharp', while pygments recognises it as 'cs' (or at least, I have to put 'cs' in the Arcanist indexed languages for the clickables to appear, while it's 'csharp' in the symbol database).
Test Plan: Tested this in my live install and it makes symbol lookup work.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley
CC: Korvin, epriestley, aran
Differential Revision: https://secure.phabricator.com/D7497