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.

Author: stnguyen90

.github/workflows/format.yml

@@ -11,7 +11,7 @@ jobs:
   format:
     runs-on: ubuntu-latest
     container:
-        image:  dart:stable
+        image: dart:stable
 
     steps:
       - name: Checkout repository
@@ -20,6 +20,9 @@ jobs:
           persist-credentials: true
           ref: ${{ github.event.pull_request.head.ref }}
 
+      - name: Install dependencies
+        run: dart pub get
+
       - name: Format Dart code
         run: dart format .