Add negative sizes as a prop pack

[felix-bohlin]

Not sure if I nailed the naming of stuff, you might want to take a look at that.

Worth noting also is that I reversed the values in each clamp and switched to logical units, ie:

--size-fluid-1: clamp(0.5rem, 1vw, 1rem); /* positive */
--size-fluid-1-: clamp(-1rem, -1vi, -0.5rem); /* negative */

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[argyleink]

what's the use case for these? do they actually produce usable values?

curious if we should instead just

--size-fluid-1-: calc(var(--size-fluid-1) * -1);

this produces the inverted value too?

[felix-bohlin]

Are you questioning the point of negative fluid sizes specifically or all of them?

Fluid is probably a more contrived situation but my thought process there was that
a) my lack of imagination how these primitives should be used shouldn't stop others from doing it
b) it wouldn't "burden" the core lib since it would be a prop pack

With that said, there's no rush here. More code is more technical debt and once you release something it's hard to take it back.

Regarding your proposition with calc though - it looks so much cleaner. Yes.