Add chapters support to Invidious

[syeopite]

This PR adds a chapters menu to the player control bar and a separate widget within the description to select chapters along with their thumbnail similar to what's on YouTube. See screenshots below.

Unfortunately, we can't segment the progress bar into multiple chunks like what YouTube does yet. VideoJS doesn't support this natively and it doesn't look like there are any extensions that does this.

Related: https://github.com/videojs/video.js/discussions/8235

Closes chapters component of #2395

[absidue]

Is there a reason you decided to create a completely new JSON API endpoint instead of just including it in the existing /api/v1/videos/{video id}? Seems like it will add extra unnecessary load on Invidious, as apps like FreeTube will be making the request for every video, but it'll frequently be pointless, as most videos don't have any chapters. Integrating it into the existing API response will make integration a lot easier.

[syeopite]

I'm not actually sure why I did that... good catch! Data for chapters should now be available in the standard /api/v1/videos/{video id} endpoint

[absidue]

Thanks!

[absidue]

Thanks!

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