[IntelliSense] Add "Sort Tailwind Classes" Source Action

[garrett-hopper]

I've written a VSCode extension which uses __unstable__loadDesignSystem and getClassOrder to automatically sort tailwind classes in Clojure hiccup style :class string and keywords. It defines a source action which can then be added to editor.codeActionsOnSave by a user to enable automatic sorting. (tailwindcss-clojure-class-sorter/blob/main/index.js#L162)

I believe such a source action would make more sense as part of the Tailwind CSS IntelliSense extension instead of being a separate extension. Its behavior would be driven by the regular expressions in tailwindCSS.experimental.classRegex (as well as the other classFunctions, classAttributes, etc.) to find classes to be sorted.

This would allow for language-agnostic completions and sorting through a single configuration instead of requiring separte configuration of IntelliSense and sorting.

Potentially this could be part of the LSP as well to support non-VSCode editors as well? I'm not very familiar with what functionality is exposed by the LSP and what is limited to only the extension.

This relates to my other discussion requesting the getClassOrder be made a public API. (#17804)