How to add custom interaction selectors?

How do I add custom interaction selectors. E.g. for an input, I would like to apply a style on this combined criteria:

.field__input:focus, .field__input:not(:placeholder-shown)

Usecase is to have a label that moves out of the way on focus, and stays out of the way when an input has content

This isn’t supported yet, but that’s an interesting case we’ll think about… For now you can rely on specifying custom CSS as an escape hatch