Add --border-color to divide theme keys

[crswll]

Summary

In Tailwind 3 the border colors were able to be used with divide utilities. I made it so that's true for Tailwind 4.

Test plan

Just used pnpm run tdd and making it fails then making sure it passes.

[rozsazoltan]

Until then, you can implement the custom namespace for your own projects:

• https://play.tailwindcss.com/6knlwB5TX2?file=css

@theme {
  --border-color-mybordercolor: #6495ED;
}

@utility divide-* {
  :where(& > :not(:last-child)) {
    border-color: --value(--border-color-*);
  }
}

[RobinMalfait]

Good catch, thanks!

[crswll]

NO PROB ROB(IN).