Add Discord Total Member Number Badge

See: badges/shields#4500 (comment)

README.md

@@ -72,7 +72,10 @@ Wechaty is an RPA (Robotic Process Automation) SDK for Chatbot Makers which can
 
 See more at [Wiki:Voice Of Developer](https://github.com/Wechaty/wechaty/wiki/Voice%20Of%20Developer)
 
-### Join Us on Discord [![Join Wechaty Discord Developer Community](https://img.shields.io/discord/916984413944967180?logo=discord&style=flat)](https://discord.gg/7q8NBZbQzt)
+### Join Us on Discord
+
+[![Join Wechaty Discord Developer Community](https://img.shields.io/discord/916984413944967180?logo=discord&style=flat)](https://discord.gg/7q8NBZbQzt)
+[![Wechaty Discord](https://img.shields.io/badge/dynamic/json?url=https%3A%2F%2Fdiscord.com%2Fapi%2Finvites%2F7q8NBZbQzt%3Fwith_counts%3Dtrue&query=%24.approximate_member_count&logo=discord&logoColor=white&label=Users%20Total&color=green&style=flat)](https://discord.gg/7q8NBZbQzt)
 
 Wechaty is used in many ChatBot projects by thousands of developers. To talk with other developers, scan the QR Code below and join our **Wechaty Developer Community**.