Update to Template for Developer Usage

Changes Made to Template:

1. Fixed BasePlayer.gd Camera Issue

• Now adds the BODY (RigidBody/KinematicBody child) to "player" group instead of parent
• Camera follows the actual moving object, not the static container
• This was the main issue we fought with during Ball Racer

2. I Made Game Names Dynamic (GameManager.gd)

• Removed hardcoded "tap_runner" and "stack_tower"
• Games auto-register when they call start_game("my_game")
• Added register_game() function for explicit registration
• Scores load from Firebase for any game name

3. I Made MenuScreen.gd Dynamic

• High score shows best across all registered games
• Leaderboard shows all registered games (not hardcoded two)

4. Added Game Name Export to GameUI.gd

• New game_name export variable in Inspector
• Set your game's name once, it's used for leaderboards automatically
• Added helpful comments explaining usage

5. Improved Player.gd Comments

• Clear documentation of three options: simple, physics-based, or BasePlayer
• Example code included

6. Created Reusable Coin System

• scripts/Coin.gd - Collectible with rotation, bobbing, sound
• scenes/Coin.tscn - Ready-to-use golden coin
• Just drag into your scene and position

7. Created QUICKSTART.md

• Step-by-step guide to making a game
• Covers player setup, level building, scoring, collectibles
• Lists all template features