Update pkg.yml

.github/workflows/pkg.yml

@@ -1,4 +1,5 @@
-# This workflow will install Python dependencies, run tests and lint with a single version of Python
+# This workflow will install Python dependencies, run tests and lint with three versions of Python
+# and three operating systems.
 # For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python
 
 name: Python application