v5.3.0 of simple_animations

Powerful package to create beautiful custom animations in no time. Changelog excerpt: - Align project constraints with the latest Flutter release baseline. (sdk: ^3.12.0, flutter: >=3.44.0and flutter_lints ^6.0.0). - Update the example app dependencies to match current Flutter project defaults. - Fix AnimationMixincompatibility with Flutter's updated TickerModeAPI. - Add regression coverage for AnimationMixinreacting to TickerModechanges. - Add widget test coverage for AnimationDeveloperTools. - Improve README quality.