Adjust gwMerge to support groundwork extensions

[jbkolze]

The current implementation of gwMerge only supports the base gw- prefix and classes without a prefix, i.e. those provided by a user. Ideally, extensions to groundwork (e.g. groundwork-water) will use their own prefixes that will also need to be supported by gwMerge.

Since v2.4, tailwind-merge supports "dynamic" prefixes that allow the user to semi-automatically account for potential prefixes as long as they fit an expected format. I propose that groundwork extensions follow a format of gw{\w*}-, e.g. gww- for groundwork-water. The gwMerge function can be upgraded to support this format and the function can be exposed as a library utility for use in its extensions.