Fix: PopScope not working with modals in Flutter 3.24+

[fujidaiti]

Related issues (optional)

Fixes #233.

Description

This PR migrates from Route.onPopInvoked to Route.onPopInvokedWithResult to address the issue. Here's a detailed explanation of this change (quoted from the README):

This package previously used the Route.onPopInvoked method to invoke PopScope.onPopInvoked callbacks when users performed a swipe-to-dismiss gesture. However, these methods were deprecated in Flutter 3.24.0 as part of a breaking change related to the PopScope widget. The problem is that ModalRoute.onPopInvoked, which was an override of Route.onPopInvoked and where PopScope.onPopInvoked callbacks were actually invoked, was removed. As a result, the PopScope.onPopInvoked callback is no longer invoked in Flutter 3.24+. These changes led to issues such as #233.

The only possible solution was to replace Route.onPopInvoked with Route.onPopInvokedWithResult, which was introduced in Flutter 3.24.0. However, migrating to the new API would require increasing the lower bound of the SDK constraint to 3.24.0. For those using an SDK version lower than 3.24, this change would be a significant breaking change. Ultimately, we decided to publish different versions for different SDK constraints to maintain backward compatibility.

Summary (check all that apply)

• Modified / added code
• Modified / added tests
• Modified / added examples
• Modified / added others (pubspec.yaml, workflows, etc...)
• Updated README
• Contains breaking changes
  • Created / updated migration guide
• Incremented version number
  • Updated CHANGELOG