Run CI on 3.10

Author: vidartf

.github/workflows/tests.yml

@@ -79,7 +79,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.6, 3.7, 3.8, 3.9, 3.10]
 
     steps:
     - uses: actions/checkout@v2