sg: introduce `sg wut` for looking up Sourcegraph acronyms and lingo
Created by: courier-new
Inspired by the wonderful @slimsag's original document WDYMWDIM, from which the dictionary definitions here are directly taken, and @muratsu's suggestion to add this to sg.
https://user-images.githubusercontent.com/8942601/152894270-a3cb7d12-dcf2-4826-9b20-d1de398429fe.mov
(My first "significant" contribution to sg here so appreciate any feedback, sorry I don't know the best person/people to tag for review!!