More minor post jam update

More minor fixes and adjustments

• Re-balanced movement speeds
• Added a splash screen
• Added a new segment to the tutorial that teaches how to bonk witches
• Tightened keyboard controls (Unity adds some gravity by default, we removed it)
• Fixed an issue where the music cuts off when getting close to the edge
• Fixed dash prompt disappearing in 16:9 aspect ratio
• Frogs are 15% happier