message: updated README to include gwg discrod invitation
diff: @@ -183,6 +183,6 @@ Sources of information:
  If you still have problems or questions, feel free to ask! Easiest ways are:
  * Open an issue on [the Github issue tracker](https://github.com/ggez/ggez/issues)
  - * Say hi on the [unofficial Rust Discord server](http://bit.ly/rust-community) or the [Rust Gamedev server](https://discord.gg/yNtPTb2)
  + * Say hi on the [unofficial Rust Discord server](http://bit.ly/rust-community), the [Rust Gamedev server](https://discord.gg/yNtPTb2) or the [good-web-game Discord server](https://discord.gg/jum3Fjek2A)
  License: MIT
  