Add python 3.10 to actions matrix now that we're off nose

.github/workflows/main.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       matrix:
         # Tested versions based on dates in https://devguide.python.org/devcycle/#end-of-life-branches, 
-        python-version: ['3.7', '3.8', '3.9']
+        python-version: ['3.7', '3.8', '3.9', '3.10']
     steps:
       - uses: actions/checkout@master
       - name: Setup python