added Code Style Fix workflow

.github/workflows/backend-code-style-fix.yml

@@ -0,0 +1,28 @@
+name: Code Style Fix
+
+on:
+  push:
+    branches: [ oasis ]
+  pull_request:
+    branches: [ oasis ]
+
+
+jobs:
+  php-cs-fixer:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.head_ref }}
+
+      - name: Run PHP CS Fixer
+        uses: docker://oskarstark/php-cs-fixer-ga
+        with:
+          args: --config=.php_cs.dist --allow-risky=yes
+
+      - name: Commit changes
+        uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          commit_message: Fix backend code styling