Fix exiting paint typing "e" in the shell

When exiting paint via the keyboard by typing "Ctrl" then "E"
separately, we consume the "key" event within paint, leaving the shell
to consume "read".

To avoid this, we run a sleep(0) to gobble any other left-over events.

Note, it's generally not enough to run a queueEvent/pullEvent here, as
the char event may not have ended up on the queue yet. Alas, as this
solution is pretty ugly.

src/main/resources/data/computercraft/lua/rom/programs/fun/advanced/paint.lua

@@ -290,6 +290,7 @@ local menu_choices = {
         return false
     end,
     Exit = function()
+        sleep(0) -- Super janky, but consumes stray "char" events from pressing Ctrl then E separately.
         return true
     end,
 }