Update GitLab CI configuration and README

Removed the coverage line from the .gitlab-ci.yml file. Also, badges for the pipeline status and coverage were added to the README file. The changes improve the information available at a glance on the project's README.

.gitlab-ci.yml

@@ -10,7 +10,6 @@ pytest:
     when: always
     reports:
       cobertura: coverage.xml
-    coverage: '/^TOTAL.*\s+(\d+\%)'
 
 pages:
   script:

README.md

+![pipeline](https://gitlab.com/%{project_path}/badges/%{default_branch}/pipeline.svg)
+![coverage](https://gitlab.com/%{project_path}/badges/%{default_branch}/coverage.svg)
+
 # Cooperative Cuisine Environment
 
 [Documentation](https://scs.pages.ub.uni-bielefeld.de/cocosy/overcooked-simulator)