Update v0.8.1 Sound effects and new skins

• Added in-game sound effects (all are optionals and can be disabled!). By default only "errors" sound effects will play, but you can enable them for all obstacle success and hearts in the "Audio" options menu.
  
• Added sound effects and animations for the hearts score animation during the post-track score overview.
  
• Added "TOO LATE" error text for failed obstacles which didn't receive their input in time. Pressing the wrong button will instead display "ERROR" (and play a different sound too), so you can distinguish between timing problems and incorrect input.
  
• Added a small timer to prevent spamming multiple "ERROR" messages and sound effects when repeatedly pressing incorrect buttons (for visual feedback purposes only, it still resets your score multiplier everytime)
  
• Adjusted floating-text popups positions and made their transitions smoother during intensity section changes
  

• Added 2 new skins: "Prototype (Inverted)" and "Black Dress"
  
• Modified all default skins to make the "shadows" on the background legs/arms much lighter
  
• Added the default hair texture to the sample hairstyle mod folder (it was missing on Windows builds)
  
• Updated the "sample skin" texture
  

• Reverted the Running section ground border to "grass", as it was better looking and the alternative didn't help with the "blur" feeling encountered by some players (as I incorrectly assumed it would).