Docs: Restructured MCP-specific documents (#7565)

### What problem does this PR solve?


### Type of change


- [x] Documentation Update

docs/develop/mcp/mcp_client_example.md

@@ -0,0 +1,16 @@
+---
+sidebar_position: 3
+slug: /mcp_client
+---
+
+# RAGFlow MCP client example
+
+We provide a *prototype* MCP client example for testing [here](https://github.com/infiniflow/ragflow/blob/main/mcp/client/client.py).
+
+:::danger IMPORTANT
+If your MCP server is running in host mode, include your acquired API key in your client's `headers` as shown below:
+```python
+async with sse_client("http://localhost:9382/sse", headers={"api_key": "YOUR_KEY_HERE"}) as streams:
+    # Rest of your code...
+```
+:::