Allow keymap layout to be configurable

[NicksPatties]

Is your feature request related to a problem? Please describe.
I would like the keymap to be adjusted to my parameters. Currently the keyboard only uses a QWERTY layout. Also the position of the enter key does not match my keyboard layout.

Additionally, in case I want to use a split keyboard, I would like the keymap to reflect the position of my keyboard more effectively.

Describe the solution you'd like
I would like to adjust this configuration via a file. Perhaps I can specify which characters are visible on my keyboard like so:

[keymap]
# A sample for DVORAK layout
keys=`1234567890[]
'<>pyfgcrl/=\
aoeuidhtns-
;qjkxbmwvz

layout="ansi"

...which then produces a keyboard layout while using sweet.

Describe alternatives you've considered
Perhaps options can be passed into the sweet command to choose a keyboard layout between ANSI or ISO.

sweet --keyboard "ansi" --layout "qwerty"

Additionally, it may be useful to configure the default behavior to either hide or show the keymap.

Additional context
When people were testing sweet this past October, some participants were not used to using QWERTY. Having a keymap that only displays QWERTY is not useful to them.