Button refactor

[MelissaAutumn]

Removing a bunch of hacks I left in, and making it so btn gives us a standard button that can be used anywhere. I need to clean it up some more so it's a draft for now but it should look exactly like how it is now.

It's a little uglier (code wise) than I'd like but we can do another pass on it later.

I've also added a little performance fix for the scrolled-nav js code. I'm not entirely sure if it's doing anything different, but I kept getting random page hitches and now it's gone so 🤷

Also I've added a --nonotes option to avoid building release notes. This greatly ^{speeds up} builds / rebuilds.

I can split up the additional changes if needed.