Some jams allow you to use non-game-specific code like a character controller or other framework components that you have previously coded.

Is that allowed here?

Sure, boilerplate is allowed. Stuff like general physics, scene management, palettes, etc. A full character controller might be pushing it a little.
Here's what the rules say:

You are allowed to set up your tools and your game engine. Tools include: palettes, fonts, tracker instruments and code libraries. Anything that is specific to a particular idea should wait until the jam starts.