Export the native platform instance for more access (especially with plugins)

[Pato05]

Is your feature request related to a problem? Please describe. It would allow for access on more options on my library just_audio_media_kit, and I'm guessing on other plugins as well.

Describe the solution you'd like Have a getter like AudioPlayer.platform or AudioPlayer.nativePlayer (with AudioPlayer being the player instance) to get the underlying AudioPlayerPlatform instance

Describe alternatives you've considered None

Additional context None