Parameterize bike festival name

[carrythebanner]

Follow-up to #914 and #916.

Portland's summer bike festival has had a few different names: Bike Summer (2002), Mini Bike Summer (2003), Pedalpalooza (2004–2021), and back to Bike Summer (2022–present). Right now the festival name is hardcoded in the content. This means that the name isn't accurate on archived pages like the Pedalpalooza 2019 calendar. Also, the code isn't as forkable for other cities since our name is hardcoded.

We could probably add the correct festival name in each page's front matter (as we already do with title), and possibly use the site config file to set a global name (for the current name, as a fallback).