Run tests on macOS 10.15 and 11.0

Author: tofi86

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
 
   tests:
     name: Run bash function tests
-    runs-on: macos-latest
+    runs-on: [ macos-10.15, macos-11.0 ]
 
     steps:
     - uses: actions/checkout@v2