Add GerritHub PolyGerrit CSS style as example has released a brand-new style inspired by the
Google's instance of Gerrit Code Review.

Make the GerritHub's style a useful example for other people
that are willing to make simple CSS themes for PolyGerrit.

Change-Id: I53f4ba09ba8241e7890862feff92f4d61067a767
(cherry picked from commit 9d37af61ed024ef38204d85f43be203751eaca21)
2 files changed