Add quotes to python version 3.10

Author: erdewit

.github/workflows/test.yml

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