Bug 1084550: Flame Ads

Custom styles to support Flame ads macro. To test, copy https://developer.allizom.org/en-US/docs/Template:flame to your local dev and involk as {{flame(0)}} or {{flame(1)}}
Merge pull request #2839 from stephaniehobson/BUG-1084550-flame-ads

Bug 1084550: Flame Ads