Frosthaven Character Boxes

This adds Frosthaven support to two of my favorite Gloomhaven Things:

* [Gloomhaven Character Box](https://www.thingiverse.com/thing:2994130) by jgrg1, or [my remix of the same](https://www.thingiverse.com/thing:4808239)
* [MagBox Dashboard and Storage](https://www.thingiverse.com/thing:3641194) by Xevin. Note that I don't know if Frosthaven classes (particularly the board/playmat) will actually fit in this design yet.

The files here are only the class-specific parts, you'll need to get the main body of both Things from the links listed above.

Each class has 3 files:

* **[class]_characterbox_lid.stl**: For use with the character boxes.
* **[class]_characterbox_icon.stl**: The icon to match the lid for the character boxes: This is sized to work with my remixed boxes, but you could resize it in the X and Y dimensions to use it with the originals.
* **[class]_magbox_icon.stl**: For use with the magbox storage/playmat.