scripts: Update keymap-render script to handle xkb keymaps too

scripts: Update keymap-render script to handle xkb keymaps too

At the moment the keyboard-render script only generates short
names for console layouts.

We're going to add /dev/input support to plymouth using
libxkbcommon, so we're going to need a list of of those keymaps
too.

This commit adds that.

Some contributions by n3rdopolis and Ray Strode.