add caretColor plugin

[Naturalclar]

Implementing #3274 #3143

add caretColor plugin that allows user to use caret-color css property.

https://developer.mozilla.org/en-US/docs/Web/CSS/caret-color

[adamwathan]

Hey! I'm open to including this but we'd want to decide what variants to enable it for (definitely responsive at least since it's that's enabled for everything, but maybe that's it?) and once we enable variants it adds a good chunk to the development file size, and that's something we are trying to be careful to avoid increasing right now.

I'm going to leave this open for now and make it something we can merge for v3.0 when we move to making @tailwindcss/jit the default engine and file size is no longer a consideration.

[adamwathan]

Hey! I've fixed this up and re-implemented it for the JIT engine only over in #4499 👍 Made sure to add you as a co-author so you get the credit for it. Going to close this one in favor of that, thank you!