Drop Python 3.7 and add 3.10 and 3.11

Python 3.7 has reached EOL and no longer receives security updates.

Author: carlthome

.github/workflows/pr.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.7, 3.8, 3.9]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
 
     steps:
       - uses: actions/checkout@v2