Skip color-mix(…) when opacity is 100%

[RobinMalfait]

This PR improves colors with alpha values where the alpha value results in 100%.

Before this change, a class like bg-red-500/100 would be generated as:

.bg-red-500\/100 {
  background-color: #ef4444;
}

@supports (color: color-mix(in lab, red, red)) {
  .bg-red-500\/100 {
    background-color: color-mix(in oklab, var(--color-red-500) 100%, transparent);
  }
}

But we don't need the color-mix, or the fallback styles at all in case the alpha value is 100%.

After this change the bg-red-500/100 class will generate as:

.bg-red-500\/100 {
  background-color: var(--color-red-500);
}

Which is essentially the same as bg-red-500, but we can migrate that away in the future. At least the generated CSS is smaller.

Test plan

1. Added a test to ensure the generated value doesn't include color-mix at all.

[thecrypticace]

These format changes seem weird

[thecrypticace]

Did Prettier update and change this or something?

[RobinMalfait]

I was too quick to quit vim and prettier didn't run in time 😂