Add coderabbit plugin to marketplace (#300)

CodeRabbit is a code review partner that provides external validation
using specialized AI architecture and 40+ integrated static analyzers.
It offers context-aware analysis and automatically incorporates project
guidelines into reviews.

Co-authored-by: Claude <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -608,6 +608,16 @@
         "url": "https://github.com/PostHog/posthog-for-claude.git"
       },
       "homepage": "https://github.com/PostHog/posthog-for-claude.git"
+    },
+    {
+      "name": "coderabbit",
+      "description": "Your code review partner. CodeRabbit provides external validation using a specialized AI architecture and 40+ integrated static analyzers—offering a different perspective that catches bugs, security vulnerabilities, logic errors, and edge cases. Context-aware analysis via AST parsing and codegraph relationships. Automatically incorporates CLAUDE.md and project coding guidelines into reviews. Useful after writing or modifying code, before commits, when implementing complex or security-sensitive logic, or when a second opinion would increase confidence in the changes. Returns specific findings with suggested fixes that can be applied immediately. Free to use.",
+      "category": "productivity",
+      "source": {
+        "source": "url",
+        "url": "https://github.com/coderabbitai/claude-plugin.git"
+      },
+      "homepage": "https://github.com/coderabbitai/claude-plugin.git"
     }
   ]
 }