Added `gifsCard` labs flag
Added `gifsCard` labs flag

refs https://github.com/TryGhost/Team/issues/1217

- labs flag for adding a gif selector in a similar fashion to our Unsplash image selector

TryGhost/Ghost,e10/Ghost,TryGhost/Ghost,ErisDS/Ghost,e10/Ghost,ErisDS/Ghost,TryGhost/Ghost,ErisDS/Ghost