chore: Allow usage of tox -e 3.15 -- <some pytest params>

Signed-off-by: Edgar Ramírez Mondragón <edgarrm358@gmail.com>

Author: edgarrmondragon

tox.ini

@@ -15,7 +15,7 @@ setenv=
     PYTHONDEVMODE=1
 commands =
     # Create HTML coverage report for humans and xml coverage report for external services.
-    coverage run --branch --source=zlib_ng -m pytest tests
+    coverage run --branch --source=zlib_ng -m pytest {posargs:tests}
     # Ignore errors during report generation. Pypy does not generate proper coverage reports.
     coverage html -i
     coverage xml -i