docs: fix README.md discord widget
**Please give a star if you like this project.**
-Join our Discord server: [![Discord](https://discordapp.com/api/guilds/562694099887587338/widget.png)](https://discord.gg/2jfycwXVM3)
+Join our Discord server: [![Discord](https://discord.com/api/guilds/562694099887587338/widget.png)](https://discord.gg/2jfycwXVM3)
It provides an easy to use, easy to deploy, easy to debug way to build
reliable Discord bots.
