Update README badges

The pipeline and coverage badges in the README file have been updated for better clarity. Instead of a single badge for every branch, there are now separate badges for the main and development branches.

README.md

-![pipeline](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/%{current_branch}/pipeline.svg)
-![coverage](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/%{current_branch}/coverage.svg)
+![main-pipeline](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/main/pipeline.svg?job=pytest&key_text=Main+Pipeline)
+![main-coverage](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/main/coverage.svg?job=pytest&key_text=Main+Coverage)
+![dev-pipeline](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/dev/pipeline.svg?job=pytest&key_text=Dev+Pipeline)
+![dev-coverage](https://gitlab.ub.uni-bielefeld.de/scs/cocosy/overcooked-simulator/badges/dev/coverage.svg?job=pytest&key_text=Dev+Coverage)
 
 # Cooperative Cuisine Environment