Added the flutter_lints to the development dependency for project 'example' (#723)

Co-authored-by: aluferau <a.luferau@gmail.com>

Author: Lufan

third_party/example/pubspec.yaml

@@ -11,6 +11,9 @@ dependencies:
   flutter_svg:
     path: ../
 
+dev_dependencies:
+  flutter_lints: ^2.0.1
+
 # The following section is specific to Flutter.
 flutter:
   uses-material-design: true