Added workflow for linters

.github/workflows/linters.yaml

@@ -0,0 +1,18 @@
+name: linters
+on: [push]
+jobs:
+  black:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Set up Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.6
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install --upgrade black
+      - name: Run linters
+        run: |
+          black --check --exclude "migrations" django_pgschemas