actions: add python code format check

Author: WangJialei-A

.github/workflows/python-format.yml

@@ -0,0 +1,28 @@
+name: Python Format
+
+on:
+  pull_request:
+    paths:
+      - '**.py'
+
+jobs:
+  python_format:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout base version
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 100
+          ref: ${{ github.event.pull_request.base.sha }}
+      
+      - name: checkout head version
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 100
+          ref: ${{ github.event.pull_request.head.sha }}
+      
+      - name: install darker
+        run: "python3 -m pip install darker"
+      
+      - name: check python format
+        run: "python3 -m darker --check --diff -r `git merge-base ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }}`...HEAD ."