ci: add flutter format check

.github/workflows/flutter-format.yml

@@ -0,0 +1,17 @@
+name: Flutter Check Format
+
+on:  
+  pull_request: {}
+  push: {}
+
+jobs:
+  release:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup Flutter
+        uses: subosito/flutter-action@v1
+        with:
+          channel: stable
+      - name: Check Dart Format
+        run: dart format --set-exit-if-changed .