docs: fix GitHub and GitLab brand capitalization

Author: Sourcegraph

README.md

@@ -22,7 +22,7 @@ A first draft specification can be found [here](https://github.com/Microsoft/lan
 In true open-source spirit the implementation is made from these parts:
 
 - The parser is generated by [Antlr4](https://www.antlr.org) from a grammar file modified from
- [this Github Gist](https://gist.github.com/ironchefpython/84380aa60871853dc86719dd598c35e4).
+ [this GitHub Gist](https://gist.github.com/ironchefpython/84380aa60871853dc86719dd598c35e4).
 
 - The protocol.go code was borrowed and modified from [lsif-go](https://github.com/sourcegraph/lsif-go).