add link in Agents MCP docs

Author: ranbel

src/content/docs/agents/model-context-protocol/mcp-portal.mdx

@@ -0,0 +1,11 @@
+---
+pcx_content_type: navigation
+title: MCP server portals
+tags:
+  - MCP
+sidebar:
+  order: 101
+external_link: /cloudflare-one/applications/configure-apps/mcp-servers/mcp-portals/
+description: Centralize multiple MCP servers onto a single endpoint and customize the tools, prompts, and resources available to users.
+
+---