Labels!

[tylersticka]

This PR introduces another front-end feature, labels.

In previous projects, we referred to this as status. To make things really extensible in the future, I thought it might make sense to borrow GitHub's "labels" vocabulary instead, and to also allow for multiple ones if we so choose.

Here's a typical use case:

But you could also use other ones (in this case, we have a style for deprecated, but none for totoro):

[lyzadanger]

:+1: We may run into additional "standard" labels as we go, but this is a great start (and simple).