* 🏷️(type) enhance QualityOptions type
Some optional properties in the QualityOptions were missing. The forced
and onChange property allwoing to use an external handler.
* ♻️(type) use Plyr.Provider for the readonly provider property
A type exists to define all available providers. This type isn't used in
the Plyr class definition and the same provider list is also defined.
This code is refactored to use the Plyr.Provider type
* 🏷️(type) add missing elements property in Plyr class
In Plyr class, you can access elements set in cache. This property is
missing in the class definition. The Plyr.Elements is for now
incomplete.
The aria-label attribute set on all play buttons does not change
according the player state. When the video is playing, the aria-label
should change to pause otherwise screen reader will not detect that this
button now can be used to pause the video.