add spawn and termcmd

treat startup command as long-running

Not quite a perfect mirror of xinit, where the startup command execs the
window manager, and the termination of that process brings down the
windowing system, but it might be the Wayland analogue.

add *.o to ignore

fix typo in comment

implement Button: movemouse, resizemouse

make Makefile a bit more my style

add CLEANMASK like dwm

make key mappings configurable in config.h

start factoring Key actions into functions

some options I like

Start with tinywl

Add a config.h into which configurables can be moved.