The code is based on prior art by
Artem Godin: https://github.com/fluorumlabs/css-variable-observer
That library only works with Custom Properties and only works with numeric values though, whereas the updated `style-observer` I created works with any property that can have any value.
Extra shout-out to @jaffathecake as well, for suggesting “some of the discrete value animation stuff” could possibly be used …
https://github.com/w3c/csswg-drafts/issues/8982#issuecomment-2317203434