Fix/playlist autoplay inactive tab

[kaustubh2332]

• Add visibilitychange listener for tab state detection
• Force next-button click on video end in hidden tabs
• Update playerOnEnded handler for background playback

[ImprovedTube]

hi and thanks! @kaustubh2332

Would like to test this soon.
Can you make "tabs" and "webnavigation" optional (requested when enabling the feature), so that they dont tirgger a warning for everybody https://developer.chrome.com/docs/extensions/reference/permissions-list
and shortly state a reason what they are used for?

(Why remove the "not a fix" comment?)