fix: prevent early dispose of CardSwiperController

[Kal-Elx]

First of all, thanks for great package 🚀

Description

I was facing the issue that the CardSwiperController I saved in my state stopped working when the CardSwiper in the child widget was rebuilt. When calling a method upon the CardSwiperController I received an error saying that the underlying stream was closed.

When investigating the code I discovered that CardSwiper is calling dispose on the CardSwiperController that was passed in as a parameter leading to the closing of the stream. My belief is that it's not the responsibility of CardSwiper to dispose of CardSwiperController since this widget did not create the controller. Instead it should be disposed by the parent widget that is passing CardSwiperController to CardSwiper, as it's done in example/lib/main.dart.

This commit fixed the issue for me.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.

[ricardodalarme]

Nice one!