Add py 3.10 to test matrix

See discussion in #463

Co-authored-by: Christian Clauss <cclauss@me.com>

Author: bennr01

.github/workflows/check-code-and-run-tests.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["2.7", "3.6"]  # TODO: Add for Pythonista v3.4 -- , "3.10"
+        python-version: ["2.7", "3.6", "3.10"]
     steps:
     - name: Checkout
       uses: actions/checkout@v3