Make package a federated plugin, so optional implemenations can be added

[Gustl22]

I propose to convert this package to a federated plugin, so developers can add more platforms, if wanted.

I may can start with a proposal PR, if wanted.

See: https://docs.flutter.dev/packages-and-plugins/developing-packages#federated-plugins

Best regards.

FYI, I really would like to see web and mobile implemented, which may is to much effort to solve it all in this package.

[lijy91]

I'm working on it #506

[Gustl22]

So cool, if you need help, let me know!