Option to do a hue-preserving invert invert(1) hue-rotate(180deg) on images in dark mode

[Artoria2e5]

Pages like https://manual.gromacs.org/current/reference-manual/algorithms/free-energy-calculations.html use a black-on-transparent diagram. This is obviously bad and is technically covered by "different images for dark/light mode", but I betcha most people will not want to find extra time to do a re-render for those cases (I mean, MathJax inverts out of the box!). Instead, I propose adding a :class: called dark-invert, which will do a hue-preserving¹ invert on dark mode:

@media (prefers-color-scheme: dark) {
    img.dark-invert, object.dark-invert{
        filter: invert(1) hue-rotate(180deg);
    }
}

There's also a possibility for light-invert but I think it would be used less often. It could be added for completeness though.

¹ Technically it does not always preserve hue as filter clips on rgb values naively. Still it's close enough for usual diagram label colors: red becomes pinkish, etc.