Adds a media session action handler for "seekto". An action handler is an event tied specifically to a common media function such as pause or play. The "seekto" action handler will be called when the site should move the playback time to a specific time. This also adds a MediaSessionActionDetails dictionary that will be passed when an action handler is called. Use this as a basis for passing additional data for "seekbackward", "seekforward" and "seekto".
We should add support for "seekto" since this action is supported by the platform and allows sites to provide a better experience.
Docs: N/A
Samples: https://beccahughes.github.io/media/media-session-seeking/index.html
Explainers: N/A