Create npmjs-readme.md

Author: kenny-y

scripts/npmjs-readme.md

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+`rclnodejs` is a Node.js client for Robot Operating System (ROS) v2.0. It provides extremely simple & easy API for ROS 2.0 programming, the following examples shows how to create a ROS 2.0 node and then publish a string message in only 6 lines of code.
+
+``` JavaScript
+const rclnodejs = require('rclnodejs');
+rclnodejs.init().then(() => {
+  const node = rclnodejs.createNode('publisher_example_node');
+  const publisher = node.createPublisher('std_msgs/msg/String', 'topic');
+  publisher.publish(`Hello ROS 2.0 from rclnodejs`);
+  rclnodejs.spin(node);
+});
+```
+
+# Install ROS 2.0
+Befire install rclnodejs, make sure ROS 2.0 is installed first. Read and follow the [Installation Guide](https://github.com/ros2/ros2/wiki/Installation) to install ROS 2.0
+
+# Install rclnodejs
+After ROS 2.0 is installed, run the following command
+
+```
+npm i --save rclnodejs
+```
+
+# More Examples
+
+Use complex message
+
+```JavaScript
+  const publisher = node.createPublisher('sensor_msgs/msg/JointState', 'topic');
+  publisher.publish({
+    header: {
+      stamp: {
+        sec: 123456,
+        nanosec: 789,
+      },
+      frame_id: 'main frame',
+    },
+    name: ['Tom', 'Jerry'],
+    position: [1, 2],
+    velocity: [2, 3],
+    effort: [4, 5, 6],
+  });
+
+```
+
+Create a subscription
+
+``` JavaScript
+const rclnodejs = require('../index.js');
+
+// Create a ROS node and then print out the string message received from publishers
+rclnodejs.init().then(() => {
+  const node = rclnodejs.createNode('subscription_example_node');
+
+  node.createSubscription('std_msgs/msg/String', 'topic', (msg) => {
+    console.log(`Received message: ${typeof msg}`, msg);
+  });
+
+  rclnodejs.spin(node);
+});
+```
+
+
+
+Create a service
+
+```JavaScript
+  node.createService('example_interfaces/srv/AddTwoInts', 'add_two_ints', (request, response) => {
+    console.log(`Incoming request: ${typeof request}`, request);
+    let result = response.template;
+    result.sum = request.a + request.b;
+    console.log(`Sending response: ${typeof result}`, result, '\n--');
+    response.send(result);
+  });
+
+```
+
+Send a request in a client
+
+```JavaScript
+  const client = node.createClient('example_interfaces/srv/AddTwoInts', 'add_two_ints');
+  const request = {
+    a: Math.floor(Math.random() * 100),
+    b: Math.floor(Math.random() * 100),
+  };
+
+  console.log(`Sending: ${typeof request}`, request);
+  client.sendRequest(request, (response) => {
+    console.log(`Result: ${typeof response}`, response);
+  });
+
+```
+
+# License
+Apache License Version 2.0
+