Update README.md (#1872)

Add discord server

README.md

@@ -5,6 +5,7 @@
 ![Version](https://img.shields.io/github/v/release/WayfireWM/wayfire)
 [![Matrix: #wayfire:matrix.org](https://img.shields.io/badge/matrix-%23wayfire%3Amatrix.org-blue)](https://matrix.to/#/#wayfire:matrix.org)
 [![IRC: #wayfire on Libera.chat](https://img.shields.io/badge/IRC-%23wayfire%20at%20libera.chat-green)](https://web.libera.chat/#wayfire)
+![Discord](https://img.shields.io/discord/1144831589877043220?label=Discord)
 [![CI](https://github.com/WayfireWM/wayfire/workflows/CI/badge.svg)](https://github.com/WayfireWM/wayfire/actions)
 [![Packaging status](https://repology.org/badge/tiny-repos/wayfire.svg)](https://repology.org/project/wayfire/versions)
 [![License](https://img.shields.io/github/license/WayfireWM/wayfire)](LICENSE)