Cleanup custom properties (#2771)

* prefix custom properties with tw-

* prefix custom properties with tw- in tests

* prefix gradient values in the defaultConfig

* inline gradient-via-color

* simplify --tw-tailwind-empty to --tw-empty

* replace the long --tw-font-variant-numeric-... to the way shorter --tw-fvn-...

* Rename --tw-box-shadow to --tw-shadow

To match class name.

* Rename font-variant-numeric variables

* Remove 'transform' from transform variables

* Shorten gradient variables

* Fix style

Co-authored-by: Adam Wathan <adam.wathan@gmail.com>

src/plugins/divideColor.js

@@ -13,7 +13,7 @@ export default function () {
         return withAlphaVariable({
           color: value,
           property: 'border-color',
-          variable: '--divide-opacity',
+          variable: '--tw-divide-opacity',
         })
       }