Change '###' to '####' in Contributing section

Author: oblomov-dev

README.md

@@ -4,7 +4,7 @@ Welcome! 👋
 
 This repository contains the source files for the [abap2UI5 documentation](https://abap2ui5.github.io/docs/).
 
-### Contributing
+#### Contributing
 
 We appreciate your help! If you spot a typo, want to improve existing content, or have ideas for new topics, feel free to open a pull request or issue.