Add ghosts + lose condition

[nucleartide]

Changelog

What does this pull request do?

• Add Pacman ghosts to scene
• Add holding pen for ghosts to start
• Add lose condition: when you touch ghosts you lose the game, and the “game over lose” UI shows
• Tech details
  • Revise PR template, small tweak
  • Add BP_GameOverLoseWidget blueprint class that derives from GameOverWidget
  • Add BP_GameOverWinWidget blueprint class that derives from GameOverWidget
  • Add BP_GateTileActor blueprint class for representing the gate in front of the ghost holding pen
  • Add BP_GhostPawn blueprint class for representing Pacman ghosts
  • Add new materials for each ghost color (Materials/MI_Solid_GhostX.uasset)

Dev Checklist

• First draft. Implement a working first pass at the feature/problem.
• Final draft. Perform a general review of Files changed and revise anything that needs to be cleaned up.
• Modularity. Review the architecture of your changes (see Unreal's Reference Viewer), and ensure modules remain decoupled.
• Build. Build the game to ensure it remains bug-free, then upload to GitHub.