Add thinkback plugin for Year in Review animation

Adds the thinkback plugin - a personalized Year in Review ASCII animation
generator for Claude Code users.

Features:
- Multiple vibes: cozy, awards show, morning news, RPG quest
- Quick generation with templates or deep dive with personalized narratives
- Comprehensive animation helpers for backgrounds, transitions, particles
- Stats extraction from Claude Code usage history

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -139,6 +139,17 @@
       "category": "development",
       "homepage": "https://github.com/anthropics/claude-plugins-public/tree/main/plugins/plugin-dev"
     },
+    {
+      "name": "thinkback",
+      "description": "Generate a personalized Year in Review ASCII animation celebrating your year with Claude Code. Features multiple vibes (cozy, awards show, morning news, RPG quest) and comprehensive animation helpers.",
+      "author": {
+        "name": "Anthropic",
+        "email": "support@anthropic.com"
+      },
+      "source": "./plugins/thinkback",
+      "category": "productivity",
+      "homepage": "https://github.com/anthropics/claude-plugins-official/tree/main/plugins/thinkback"
+    },
     {
       "name": "greptile",
       "description": "AI-powered codebase search and understanding. Query your repositories using natural language to find relevant code, understand dependencies, and get contextual answers about your codebase architecture.",