Fix readme layout

Author: JonJagger

README.md

@@ -1,6 +1,6 @@
 [![Github Action (master)](https://github.com/cyber-dojo-languages/clangplusplus-cgreen/actions/workflows/main.yml/badge.svg)](https://github.com/cyber-dojo-languages/clangplusplus-cgreen/actions)
 
-### display_name="C++ (clang++ 18.1.3), Cgreen 1.6.3"
+## display_name="C++ (clang++ 18.1.3), Cgreen 1.6.3"
 ## image_name="ghcr.io/cyber-dojo-languages/clangpp_cgreen"
 
 ![cyber-dojo.org home page](https://github.com/cyber-dojo/cyber-dojo/blob/master/shared/home_page_snapshot.png)