Make panels unfoldable or scrollable

[dascritch]

On very long WebVTT files, do able via attributes to

• [x] have a unfoldable panel (both click and key for a11y)
• [ ] have a panel with a maximum height using both WC attribute and CSS variable
• [ ] have a panel with a maximum height scrolled by highlight_point()

[dascritch]

Or even, resizable ? https://spin.atomicobject.com/2019/11/21/creating-a-resizable-html-element/

[dascritch]

Scrollables elements inside scrollable elements (webpage) is a very bad idea.

Instead, we can use position:sticky, which is really easier and really mobile friendly. I think about a very long chapter panel, as in https://dascritch.net/post/2017/12/14/CPU-Ex0069-Bonsoir-%C3%A0-vous%2C-entre-IA%2C-p%C3%A9riph%C3%A9riques-et-adultes-consentants The main difficult task will be to not display panels under the main element, but still keeping semi-transparent capabilities

Unfoldable may still be interesting, but should be done only for a theme, I believe.

[dascritch]

May be the best way is to declare panels as <details><summary> ?