wait a little to flush disk before quitting

I've been noticing in pensieve.love in particular that once a month or
so I lose data if I quit immediately after typing in something. Nothing
major, just the odd link between notes which leaves things in an
inconsistent state. Let's see if this helps.

edit.lua

@@ -192,6 +192,8 @@ function edit.quit(State)
   -- make sure to save before quitting
   if State.next_save then
     save_to_disk(State)
+    -- give some time for the OS to flush everything to disk
+    love.timer.sleep(0.1)
   end
 end