add python 3.10 to version matrix (#436)

Author: kaczmarj

.github/workflows/pull-request.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        python-version: ['3.9', '3.8', '3.7']
+        python-version: ['3.10', '3.9', '3.8', '3.7']
     steps:
       - name: Install Singularity
         run: |