Levels update

• Added 0-21 and 0-22. This update gives another route to clear w0.
  
• Changed 9-4.
  
• Adjusted 8-2 and 8-13, and swapped 8-5 and 8-B so that it is easier to solve the normal levels of w8.
  
• Fixed 0-15 to prevent unintended solutions.
  
• Adjusted some levels. (This does not affect the solutions.)
  

Other changes

• Added options to change the colors of hot and cold.
  
• Added an option to change the appearance of sticky sides. This option becomes available by clearing 2-1.