* With the Window Manager update you can open the Level Settings window
while editing a level, to change its wallpaper or page type. But you
could "draw" in the level "through" the opened window. This bug is now
fixed: if the cursor is on top of a managed UI window, the Canvas loop
is not called.
* Take advantage of the new Window Manager feature of the UI toolkit.
* Move the MenuScene's "New Level" and "Play/Edit Level" windows into
stand-alone functions in new pkg/windows/ package. The 'windows'
package is isolated from the rest of Doodle and communicates using
config variables and callback functions to avoid circular dependency.
* MenuScene calls the window constructors from the new package.
* Add an "Options" button to the Menu Bar in the Editor Scene, which
opens the "New Level" window to allow changing the wallpaper or
bounding type of the level currently being edited.
* Move the cheat codes into their own file, cheats.go