Better Game Summary Cards

The game summaries on the front page now have their own styling! Right now, it can only be used on a markdown page. The following code is an example card:

> ## [Game Title](/games/game-name)
> **System:** System Name
> **GM:** GM's name
> **Summary:** A brief summary or pitch for the game.
> Keep it to a few short sentences.
{.is-game}

And it renders as this card:

Screen Shot 2020-08-19 at 14.15.48.png