Can be used to as for confirmation for actions (E.g. shut down pc,
reboot and so on). Takes 3 parameters, with the last being optional, in
the form of:
dmenuprompt "Text to display" "command to execute on yes"
[success/warn/danger]
The last flag only changes the colors being displayed by the prompt.
If the last flag is not provided, it will display in default colors.
