Shadow position classes

[Soviut]

Currently, the shadow and drop-shadow have very specific vertical offsets that corresponds to their size. I propose that shadow-x-<length> and shadow-y-<length> be added to these can be adjusted manually.

I specifically want to be able to set them to 0 so the shadow appears evenly around every edge, like this:

I know that the effect is possible by extending the theme or using arbitrary values, but that means having to specify all attributes of the shadow, losing out on reuse of the tailwind shadows.