The thumb cluster maps a little goofy and I'd like to clean up the
keymap here - it's ENTIRELY NOT OBVIOUS how this works right now. Using
this keymap as an example, the physical layout of my thumb cluster is
actually:
Far left: Left
Next to the right: Right
Bottom right: Shift
Top right: MO(2)
You can see what this maps to in code, and it's not at all intuitive.
`swap_indicies`, which we already support, is useless here because,
unlike the Planck/Klaranck, these aren't 1:1 key swaps, but an entirely
custom mapping of columns. This will require something like QMK's
solution to fully custom (or at least partially custom) keymaps at a
core level, and isn't something I feel like tackling tonight
necessarily.
