This module provides support for the keymap command. This command
accepts one parameter to specify either the layout_name or the
filename.
When specifying the layout_name, this command will attempt to open the
GRUB keymap file based on the following logic:
Get the "prefix" from environment variable prefix
Open keymap file prefix/layouts/layout_name.gkb
When specifying the filename, the full path to the ".gkb" file should be provided. The ".gkb" file can be generated by grub-kbdcomp.