Add concurrency to not waste precious build minutes when modifying PRs frequently. (#1051)

Co-authored-by: wkpark <wkpark@gmail.com>

.github/workflows/python-package.yml

@@ -15,10 +15,13 @@ on:
       - 'setup.py'
       - 'pyproject.toml'
       - 'pytest.ini'
-      - '**/*.md'
   release:
     types: [ published ]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   ##