Test matrix covers Python 3.11

Author: rayluo

.github/workflows/python-package.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, "3.10"]
+        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, "3.10", "3.11.0-alpha.5"]
 
     steps:
     - uses: actions/checkout@v2