Add caret classes

[ben-rogerson]

This PR adds the following types of caret color classes:

tw`caret-red-500`; // Color classes
tw`caret-red-500/20`; // Color alpha classes
tw`caret-[color:blue]`; // Coerced arbitrary classes
tw`caret-[red]`; // Arbitrary classes

// ↓ ↓ ↓ ↓ ↓ ↓

({
  "caretColor": "rgba(239, 68, 68, 0.2)"
});
({
  "caretColor": "#ef4444"
});
({
  "caretColor": "blue"
});
({
  "caretColor": "red"
});