ci: Test tmux 3.2b

Author: tony

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         python-version: ["2.7", "3.x"]
-        tmux-version: ["2.6", "2.7", "2.8", "3.0a", "3.1b", "master"]
+        tmux-version: ["2.6", "2.7", "2.8", "3.0a", "3.1b", "3.2b", "master"]
     steps:
       - uses: actions/checkout@v1