Fix linter violations

[ootsamo]

Fixes the following linting warnings:

   info • The imported package 'wolt_modal_sheet' isn't a dependency of the importing package • example/lib/main.dart:2:8 • depend_on_referenced_packages
   info • The import of 'package:flutter/foundation.dart' is unnecessary because all of the used elements are also provided by the import of 'package:flutter/material.dart' •
          lib/src/content/components/main_content/wolt_modal_sheet_top_bar.dart:1:8 • unnecessary_import
warning • Unused import: 'package:wolt_modal_sheet/src/modal_page/wolt_modal_sheet_page.dart' • lib/src/content/components/main_content/wolt_modal_sheet_top_bar.dart:3:8 • unused_import
warning • Unused import: 'package:wolt_modal_sheet/src/utils/wolt_layout_transformation_utils.dart' • lib/src/content/components/main_content/wolt_modal_sheet_top_bar.dart:4:8 • unused_import
warning • Unused import: 'package:demo_ui_components/demo_ui_components.dart' • playground_navigator2/lib/router/playground_router_delegate.dart:3:8 • unused_import
   info • The imported package 'wolt_responsive_layout_grid' isn't a dependency of the importing package • playground_navigator2/lib/router/playground_router_delegate.dart:12:8 •
          depend_on_referenced_packages
warning • Unused import: 'package:wolt_responsive_layout_grid/wolt_responsive_layout_grid.dart' • playground_navigator2/lib/router/playground_router_delegate.dart:12:8 • unused_import

[ulusoyca]

Thanks for fixing these @ootsamo