Fix achievement progression by moving Whispering Woods unlock

🎯 Achievement System Improvements:
- Pet Collector achievement (5 pets) now unlocks Whispering Woods
- Nature Explorer achievement (3 Grass species) no longer unlocks location
- Added 2 new Grass-type pets: Vinewrap and Bloomtail
- Updated Whispering Woods spawns to include new Grass pets

🐛 Problem Solved:
- Broke the catch-22 where players needed achievements to access locations
- But needed species from those locations to earn achievements
- Now players can progress naturally: 5 pets → Whispering Woods → more Grass species

🆕 New Pets:
- Vinewrap (Grass) - Defensive grass pet with vine abilities
- Bloomtail (Grass) - Fast grass pet with flower-based attacks

🔧 Updated Spawns:
- Whispering Woods: 3 Grass species (Leafy, Vinewrap, Bloomtail) + rare Flamey
- Players can now complete Nature Explorer achievement after accessing Whispering Woods

📚 Documentation:
- Updated README with new achievement progression
- Clarified unlock sequence and achievement relationships

This change makes the game progression much more logical and accessible for new players.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

config/achievements.json

@@ -4,7 +4,7 @@
         "description": "Catch 3 different Grass-type pets",
         "requirement_type": "catch_type",
         "requirement_data": "3:Grass",
-        "unlock_location": "Whispering Woods"
+        "unlock_location": null
     },
     {
         "name": "Spark Collector", 
@@ -39,7 +39,7 @@
         "description": "Catch your first 5 pets",
         "requirement_type": "catch_total",
         "requirement_data": "5",
-        "unlock_location": null
+        "unlock_location": "Whispering Woods"
     },
     {
         "name": "Advanced Trainer",