fixing third bug in ci.yml

Author: MilosAtz

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ${{ matrix.os.runs-on }}
     strategy:
       matrix:
-        python-version: 3.6
+        python-version: "3.6"
         os:
           -   name: Linux
               runs-on: ubuntu-20.04
@@ -62,7 +62,7 @@ jobs:
     runs-on: ${{ matrix.os.runs-on }}
     strategy:
       matrix:
-        python-version: [3.6]
+        python-version: ["3.7", "3.8"]
         os:
           -   name: Linux
               runs-on: ubuntu-latest