Adding Python 3.10 to CI jobs

Author: mwatts15

.github/workflows/python-package.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [2.7, 3.7, 3.8, 3.9]
+        python-version: [2.7, 3.7, 3.8, 3.9, '3.10']
         database:
         - pgsql
         - mysql