Apparantly, after activating numlock once, the numlock modifier
stays turned on (use xev(1) to verify). So, to resolve useful
keysyms, we remove the numlock flag from the event state. What
currently does not work is actually using your keypad.
Commands are 'mark' and 'goto'. Both can be used either directly,
like 'mark a' and 'goto a', or interactively (just 'mark'). For
interactive mode, i3-input must be installed and in your PATH.