ci: Add test config for 3.10

Author: dbanty

.github/workflows/checks.yml

@@ -13,10 +13,9 @@ jobs:
   test:
     strategy:
       matrix:
-        python: [ 3.6, 3.7, 3.8, 3.9 ]
+        python: [ 3.6, 3.7, 3.8, 3.9, 3.10.0-beta.3 ]
         os: [ ubuntu-latest, macos-latest ]
     runs-on: ${{ matrix.os }}
-
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python