Add external plugin rayfin (#2840)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

.github/plugin/marketplace.json

@@ -1291,6 +1291,32 @@
       "description": "Complete toolkit for building Model Context Protocol (MCP) servers in Python using the official SDK with FastMCP. Includes instructions for best practices, a prompt for generating servers, and an expert chat mode for guidance.",
       "version": "1.0.0"
     },
+    {
+      "name": "rayfin",
+      "description": "Getting-started router skill for Rayfin - scaffold a new app with the Rayfin CLI, then use the version-locked skill installed in the project.",
+      "version": "0.3.0",
+      "author": {
+        "name": "Microsoft",
+        "url": "https://www.microsoft.com"
+      },
+      "repository": "https://github.com/microsoft/rayfin",
+      "homepage": "https://github.com/microsoft/rayfin",
+      "license": "MIT",
+      "keywords": [
+        "rayfin",
+        "getting-started",
+        "scaffold",
+        "create-rayfin",
+        "rayfin-cli",
+        "fabric",
+        "typescript"
+      ],
+      "source": {
+        "source": "github",
+        "repo": "microsoft/rayfin",
+        "ref": "plugin-v0.3.0"
+      }
+    },
     {
       "name": "react18-upgrade",
       "source": "plugins/react18-upgrade",