docs: add new rule idea no-unnecessary-arbitrary-value

Author: francoismassart

README.md

@@ -221,5 +221,8 @@ The plugin will look for each setting in this order and stops searching as soon
 - `no-redundant-variant`: e.g. avoid `mx-5 sm:mx-5`, no need to redefine `mx` in `sm:` variant as it uses the same value (`5`)
 
 - `only-valid-arbitrary-values`:
+
   - e.g. avoid `top-[42]`, only `0` value can be unitless.
   - e.g. avoid `text-[rgba(10%,20%,30,50%)]`, can't mix `%` and `0-255`.
+
+- `no-unnecessary-arbitrary-value`: e.g. replacing `h-[0]` by its configuration based classname `h-0`.