add lint ci

.github/workflows/lint.yml

@@ -0,0 +1,13 @@
+name: Lint
+
+on: [push, pull_request]
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Backend code formatting check (Black)
+        uses: psf/black@stable