[FEATURE REQUEST] Add support for flutter web

[mariyabytes]

Is your feature request related to a problem? Please describe.
Right now, there is no good way to embed a youtube video in a flutter webapp. I've used this plugin extensively on Android and IOS, really satisfied with it.

Describe the solution you'd like
If possible, add support for an iframe / webview based youtube player with the same UI that we can embed as a widget. Right now, if I try to run the youtube player on web, get this error :

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following UnsupportedError was thrown building RawYoutubePlayer(dirty, dependencies:
[InheritedYoutubePlayer], state: _RawYoutubePlayerState#63a90):
Unsupported operation: Platform._operatingSystem
The relevant error-causing widget was:
  RawYoutubePlayer

Describe alternatives you've considered
I've tried embedding youtube's official embed player in an iframe but it doesn't seem to work for me.

[sarbagyastha]

Duplicate of #58.