v0.2.5 Updates

Focused mainly on things not in the demo:

• Ending world/level (involving unlocking infinite resources mode)
• Several new and refined levels in worlds 2-4

Several bugs fixes caught from a bought of playtestings:

• Race condition when simultaneously pressing undo and redo
• Can undo a broader class of irreversible jumps
• Make sure won't collect a pickup immediately after undo
• More accurate detection of when the player is overlapping a potential cube (and when they can be automatically placed on top)
• Bug with entering world gate after trying to move in an invalid  direction