Bring changes in https://github.com/shareef-dweikat/flutter-intro-slider upstream

[wuan]

We have forked that repo during the development and should have a look on how to bring those changes upstream.

[donpui]

@shareef-dweikat maybe you can comment on changes it self. To my understanding, we modified flutter-intro-slider to make our own intro pages with our styles, buttons and names

[donpui]

Additionally we should think, that maybe all these forks should be consolidated under LeastAuthority organisation

[donpui]

One more, we need also to downstream before upstreaming anything, because we already cannot update some plugins, because of this plugin dependencies to older packages.

[wuan]

Additionally we should think, that maybe all these forks should be consolidated under LeastAuthority organisation

I would first like to investigate to upstream all the features we added to reduce maintenance on our side.

[donpui]

We need @shareef-dweikat here. Diff from upstream https://github.com/duytq94/flutter-intro-slider/compare/master...shareef-dweikat:flutter-intro-slider:master?diff=split

FYI @ewanas