Support and test Python 3.10

Change-Id: I0dfbabc870017f6813884be6d4f6c6723a3a527b
diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index 6ca2b73..3c235c7 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -7,10 +7,10 @@
 
     runs-on: ${{ matrix.os }}
     strategy:
-      max-parallel: 4
+      max-parallel: 6
       fail-fast: false
       matrix:
-        python-version: [3.9]
+        python-version: [3.9, 3.10]
         r-version: [release]
         os: [windows-latest, macOS-latest, ubuntu-latest]
     steps: