add format checker

.github/workflow/lints.yaml

@@ -0,0 +1,31 @@
+name: Lints
+
+on:
+  push:
+    branches:
+      - main
+  pull_request: {}
+
+jobs:
+  lints:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.7
+
+      - name: Black
+        uses: psf/black@stable
+        with:
+          args: ". --check --diff"
+
+      - name: flake8
+        run: |
+          python -m pip install --upgrade pip
+          pip install flake8
+          flake8 .