Add async-timeout to requirements in setup.py

The async-timeout Python package was added to the list of requirements in setup.py. This new dependency is required for the correct functioning of some asynchronous operations in the application.

setup.py

@@ -11,7 +11,7 @@ with open('CHANGELOG.md') as history_file:
     history = history_file.read()
 
 requirements = ["aaambos @ git+https://gitlab.ub.uni-bielefeld.de/scs/aaambos/aaambos@main",
-                "websockets"]
+                "websockets", "async-timeout"]
 
 test_requirements = ['pytest>=3', ]