fix: add missing GitHub Codespaces badge to README.md

Author: RealVishy

README.md

@@ -2,4 +2,6 @@
 
 The repository for the upcoming Docker Workshop
 
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/ProgSoc/Docker-Workshop)
+
 [![Docker Workshop Wiki](https://img.shields.io/badge/Wiki-Docker%20Workshop-blue?style=for-the-badge&logo=github)](https://github.com/ProgSoc/Docker-Workshop/wiki)