feat: 🎸 hello world section

Author: hcfw007

docusaurus/docs/api/hello-world.md

@@ -0,0 +1,40 @@
+---
+title: Hello World
+sidebar_label: 'Hello World'
+---
+
+## Hello World
+
+In this section, we'll create a simple bot: Ding-Dong bot. When it receives a text message 'ding', it will reply with text 'dong'.
+
+1. install dependencies with npm
+
+    ```bash
+    npm install wechaty
+    ```
+
+2. create a bot instance
+
+    ```ts
+    import { WechatyBuilder } from 'wechaty'
+
+    const bot = new WechatyBuilder.build()
+    ```
+
+3. listen to scan event
+
+    ```ts
+    bot.on('scan', (qrcode, status) => console.log(`Scan QR Code to login: ${status}\nhttps://wechaty.js.org/qrcode/${encodeURIComponent(qrcode)}`))
+    ```
+
+    As we know, each QRcode represents a particular string. Here the call back of scan event will pass a qrcode string. We generate the qrcode with wechaty website api and scan to login.
+
+4. listen to message event
+
+    ```ts
+    bot.on('message', message => if (message.text() === 'ding') {
+      message.say('dong')
+    })
+    ```
+
+    The message event will pass a ```MessageInterface``` instance to the callback. We can get the text content by calling ```message.text()```. If the message is 'ding', we reply with ```message.say()```. This is a shortcut for sending messages to the sender of the message. You can find detail info about it in [User-Module: Message](api/message.md) section.

docusaurus/sidebars.ts

@@ -22,6 +22,7 @@ const api: SubMenuData = {
   label: 'API',
   items: [
     'api/overview',
+    'api/hello-world',
     'api/wechaty',
     'api/message',
     'api/contact',