Add Python 3.11 release candidate to the testing

Author: cclauss

.github/workflows/ci.yaml

@@ -68,7 +68,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.7, 3.8, 3.9, "3.10"]
+        python-version: [3.7, 3.8, 3.9, "3.10", "3.11-dev"]
         os: [MacOS, Ubuntu, Windows]
 
     steps: