fix: install dependencies so analysis options work during format

Because the flutter_lints dev dependency wasn't installed, dart format couldn't resolve the analysis_options.yaml properly and didn't fully format everything correctly.

.github/workflows/format.yml

@@ -10,8 +10,6 @@ on:
 jobs:
   format:
     runs-on: ubuntu-latest
-    container:
-        image:  dart:stable
 
     steps:
       - name: Checkout repository
@@ -19,6 +17,14 @@ jobs:
         with:
           persist-credentials: true
           ref: ${{ github.event.pull_request.head.ref }}
+      
+      - name: Install Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+
+      - name: Install dependencies
+        run: flutter pub get
 
       - name: Format Dart code
         run: dart format .