docs: add usage examples for Node.js in README to facilitate quick start with HackMD API

Author: Yukaii

README.md

@@ -6,6 +6,30 @@ This repository contains a set of packages for interacting with the [HackMD API]
 
 See [README](./nodejs)
 
+## Examples
+
+To help you get started quickly, we provide comprehensive usage examples in the `examples/` directory:
+
+### Node.js Example
+
+The `examples/nodejs/` directory contains a complete example project demonstrating:
+
+- User information retrieval
+- Note creation and management
+- ETag support for caching
+- Content updates
+- Error handling with retry logic
+- Environment variable configuration
+
+To run the Node.js example:
+
+1. Navigate to the example directory: `cd examples/nodejs`
+2. Follow the setup instructions in [examples/nodejs/README.md](./examples/nodejs/README.md)
+3. Set your HackMD access token
+4. Run `npm start`
+
+The example includes detailed comments and demonstrates best practices for using the HackMD API client.
+
 ## LICENSE
 
 MIT