Move HotImport related code to a Plugin
Created by: huan
We do not want to support HotImport in Wechaty any more.
After this issue was finished:
import { HotEventHandlers } from 'wechaty-plugin-contrib'
const bot = new Wechaty()
bot.use(HotEventHandlers({
'message': './handlers/message',
'friendship': './handlers/friendship',
}))