TL;DR: I made a 2D platformer character controller for Godot that you can find here
I know general-purpose code like movement scripts are allowed to be worked on prior to the jam starting but I still felt like I was cheating while working on the base character controller for my planned platformer, so I wanted to share it with anyone here that might be working with Godot and is in need of one! It's not perfect but I described what I could in the comments, it supports jump buffering and coyote time as well as sprinting and jump canceling. Most of if not all the used values are exported, so you can just slap the script onto your character or extend it and fiddle with the values in the inspector, and the majority of the logic is abstracted into functions you can override in your own class for better control.
Hope this helps someone, good luck to everyone participating!