Biff coding #8: Platypub UI improvements

We're doing a pair programming session with Winston Novo.
We'll take out one or two of the good-first-issues on Platypub's roadmap, perhaps starting with #12: Use select component for theme. RSVP for access to the Zoom link.

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Periodically we hack on a Biff project together. We'll do a pair programming session if anyone has signed up; otherwise I'll do a solo coding session. Either way it'll be relaxed, no preparation needed. Afterwards we can chat if anyone has anything to talk about.

All meetups will be held on Zoom. We'll record the coding session, and the post-coding chat part will be unrecorded.