Add Python 3.10 CI build (#45)

.github/workflows/tests.yml

@@ -7,12 +7,12 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python: [3.6, 3.7, 3.8, 3.9]
+        python: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         os: [ubuntu-18.04, windows-2016]
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python }}
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python }}
       - name: Setup VC