Add python 3.10 to matrix of github tests

Author: tiagocoutinho

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.7, 3.8, 3.9]
+        python-version: [3.7, 3.8, 3.9, "3.10"]
     steps:
     - name: Checkout
       uses: actions/checkout@v2