Add Python 3.10 to test matrix

Author: necaris

.github/workflows/tests.yaml

@@ -17,8 +17,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
-        os: [ubuntu-20.04, macos-latest, windows-latest]
+        python-version: [3.6, 3.7, 3.8, 3.9, 3.10]
+        os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
     - uses: actions/checkout@master
     - uses: actions/setup-python@v2