Add `github` build folder to Git ignore file.
Add `github` build folder to Git ignore file.

chrisdone/haskellnews,chrisdone/haskellnews,haskellnews/haskellnews,lwm/haskellnews,jwaldmann/haskellnews,lwm/haskellnews,jwaldmann/haskellnews,haskellnews/haskellnews