Null Safety?

[darkfrog26]

Any intentions to upgrade this to support null safety? I'd like to use this library, but my project requires all libraries to have null safety support.

[JasCodes]

Maybe at some point in future. But really busy atm. You are free to send PR meanwhile.

And to be honest it requires rewrite as it interrupt animation when states changes. Not an optimal arrangement.

[LowLevelSubmarine]

Created a PR: #4