make documentation screenshots interactive: different styles, click on controls/widgets to jump to docs

The idea is to begin on this page https://doc-snapshots.qt.io/qt6-dev/qtquickcontrols-index.html which has this rendering:

and rather just show one style at a time, but have some sort of non-JS HTML controls (such as tabs or a combobox) to switch between styles, and a way of trying out dark mode too.

Also, each screenshot should become an image map, so that if you click on the visual representation of a Slider, it takes you to the Slider docs, etc. Each screenshot should be a fairly complete gallery so that you can get to most of the Controls docs this way.

The reason to use HTML/CSS with no JS is so that there is some hope that qlitehtml would be able to implement these interactive features.