docs: add guide on building custom extensions (#806)

examples/mcp-wiki/README.md

@@ -0,0 +1,59 @@
+# MCP Server to read Wikipedia Article
+
+### Test using MCP Inspector
+
+1. Install venv and package dependencies:
+
+```bash
+uv sync
+```
+
+2. Activate your virtual environment:
+
+```bash
+source .venv/bin/activate
+```
+
+3. Run your server in development mode:
+
+```bash
+mcp dev src/mcp_wiki/server.py
+```
+
+4. Go to `http://localhost:5173` in your browser to open the MCP Inspector UI.
+
+5. In the UI, you can click "Connect" to initialize your MCP server. Then click on "Tools" tab > "List Tools" and you should see the `read_wikipedia_article` tool. 
+Then you can try to call the `read_wikipedia_article` tool with URL set to "https://en.wikipedia.org/wiki/Bangladesh" and click "Run Tool". 
+
+### Testing the CLI
+
+1. Install your project locally:
+
+```bash
+uv pip install .
+```
+
+2. Check the executable in your virtual environment:
+
+```bash
+ls .venv/bin/  # Verify your CLI is available
+```
+
+3. Test the CLI:
+
+```bash
+mcp-wiki --help
+```
+
+You should see output similar to:
+
+```plaintext
+❯ mcp-wiki --help
+usage: mcp-wiki [-h]
+
+Gives you the ability to read Wikipedia articles and convert them to Markdown.
+
+options:
+ -h, --help  show this help message and exit
+```
+