added github action to check code format with black

.github/workflows/code-format.yml

@@ -0,0 +1,16 @@
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-18.04
+    steps:
+    - uses: actions/checkout@v1
+    - uses: actions/setup-python@v1
+      with:
+        python-version: 3.7
+    - run: pip install --upgrade pipenv>=2018.10.9
+    - run: pipenv install --deploy --dev
+    - run: pipenv graph
+    - run: pipenv run black --check .