Add favicon to pdoc command in GitLab CI configuration

Added a favicon parameter to the pdoc command in the .gitlab-ci.yml file. This results in the favicon being specified during the documentation generation process. This change should improve the importance of the favicon when the documentation is viewed in a browser tab.

.gitlab-ci.yml

@@ -18,7 +18,7 @@ pages:
     - apt-get install -y python3-dev python3-pip graphviz graphviz-dev
     - pip install pdoc
     - pip install ".[rl]"
-    - pdoc --output-dir public cooperative_cuisine !cooperative_cuisine.reinforcement_learning --logo https://gitlab.ub.uni-bielefeld.de/uploads/-/system/project/avatar/6780/Cooking-Vector-Illustration-Icon-Graphics-4267218-1-580x435.jpg --docformat google
+    - pdoc --output-dir public cooperative_cuisine !cooperative_cuisine.reinforcement_learning --logo https://gitlab.ub.uni-bielefeld.de/uploads/-/system/project/avatar/6780/Cooking-Vector-Illustration-Icon-Graphics-4267218-1-580x435.jpg --docformat google --favicon cooperative_cuisine/pygame_2d_vis/images/favicon.ico
   artifacts:
     paths:
       - public