Support dart native

[guyluz11]

In my case I'm casting from Dart server so it is dart native without flutter

I found a package that supports dart native and added some features in my fork

https://github.com/guyluz11/flutter_cast.git Branch: multicast_version

First of all you can take a look at my code and the example, it may help you add new features that I've already implemented and are missing.

Actually I found online a way to cast YouTube videos but the implementation isn't complete yet.

So if you would like to join forces and collaborate it would be lovely.