ci(tests): Add tmux 3.3a

Author: tony

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         python-version: [ '3.10' ]
-        tmux-version: [ '2.6', '2.7', '2.8', '3.0a', '3.1b', '3.2a', 'master' ]
+        tmux-version: [ '2.6', '2.7', '2.8', '3.0a', '3.1b', '3.2a', '3.3a', 'master' ]
         # balance ci coverage across supported python/tmux versions with CI speed
         include:
           - python-version: '3.7'