added wechaty-class section

docusaurus/docs/api/wechaty-class.md

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+## Classes
+
+### Wechaty
+
+Wechaty is the main bot class.
+
+A `Bot` is a wechat client that  depends on which  type of puppet is used. The form the Bot takes is widely divided into 3 main categories-
+
+* **web-wechat** - when Puppet-Puppeteer or Puppet-wechat4u is used  
+* **ipad-wechat** - when Puppet-padchat is used
+* **ios-wechat** - when  Puppet-ioscat is used
+
+To understand puppet and its uses do visit the below link-
+
+### [What is a Puppet in Wechaty](https://github.com/wechaty/wechaty-getting-started/wiki/FAQ-EN#31-what-is-a-puppet-in-wechaty)?
+
+> If you want to know how to send message, see Message
+> If you want to know how to get contact, see Contact