Improve arbitrary value support

[ben-rogerson]

This PR adds improved and wider support for arbitrary values over a variety of classes.

For example, here some of the hints we can now use on bg which will force the matching property to be used for the output:

tw`bg-[url:url('/img/hero-pattern.svg')]`
tw`bg-[position:200px 100px]`
tw`bg-[image:custom]`

Typehint suggestions

Twin will suggest a list of all the possible typehinted classes if you get one wrong, eg:

tw`bg-[asd:url('/img/hero-pattern.svg')]`

// ↓ ↓ ↓ ↓ ↓ ↓

✕ Bad: `bg-[asd:url('/img/hero.svg')]` < The coerced value of “asd” isn’t available
✓ Good: Try one of these coerced classes:

`bg-[color:url('/img/hero.svg')]` to use `backgroundColor`
`bg-[url:url('/img/hero.svg')]` to use `backgroundImage`
`bg-[image:url('/img/hero.svg')]` to use `backgroundImage`
`bg-[position:url('/img/hero.svg')]` to use `backgroundPosition`
`bg-[length:url('/img/hero.svg')]` to use `backgroundSize`
`bg-[percentage:url('/img/hero.svg')]` to use `backgroundPosition`

Plain arbitrary values

Values without typehints (eg: bg-[200px]) will be validated against each of the possible typehints defined on the class in order to guess the correct property to use.
For example: bg-[200px] will use the backgroundPosition property and bg[url(...)] will use backgroundImage.

Notes

• This PR includes Support all color values from CSS Colors Level 4 spec tailwindlabs/tailwindcss#5154
• You can now use underscores to indicate a space within Arbitrary values - just as tailwind requires, eg: bg-[200px_100px]