Add mongodb plugin (#1095)

Official MongoDB plugin (MCP Server + Skills) from mongodb/agent-skills.
Partner escalation — submitted via PR #158, Forge, and Slack.
Already merged on -internal (PR #667).

.claude-plugin/marketplace.json

@@ -749,6 +749,17 @@
       },
       "homepage": "https://www.mintlify.com/"
     },
+    {
+      "name": "mongodb",
+      "description": "Official Claude plugin for MongoDB (MCP Server + Skills). Connect to databases, explore data, manage collections, optimize queries, generate reliable code, implement best practices, develop advanced features, and more.",
+      "category": "database",
+      "source": {
+        "source": "url",
+        "url": "https://github.com/mongodb/agent-skills.git",
+        "sha": "c47079f65e88a113c52d1ce0618684cef300246c"
+      },
+      "homepage": "https://www.mongodb.com/docs/mcp-server/overview/"
+    },
     {
       "name": "neon",
       "description": "Manage your Neon projects and databases with the neon-postgres agent skill and the Neon MCP Server.",