frontend/feat: Added Flutter workflow

.github/workflows/cross_native.yml

@@ -0,0 +1,27 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: Dart
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    defaults:
+      run:
+        working-directory: Frontend/cross_native/
+    steps:
+      - uses: actions/checkout@v3
+      - name: Flutter action
+        uses: subosito/[email protected]
+        with:
+          channel: stable
+      - run: flutter build apk