Utilities map configuration functions

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

It'd be great if Bootstrap was providing functions or mixins to manipulate that utilities hash a bit more easily. I'm thinking something like:

• utilities-add-values($utility-name, $values) for adding values to a specific utility
• utilities-set-values($utility-name, $values) for replacing the values of a utility completely
• utilities-remove-values($utility-name, $values) for removing targeted values of a utility
• utilities-set-options($utility-name, $options) to set specific options like responsive
• utilities-add($new-utility-name, $options) to add a new utility class
• utilities-remove($utility-name) to completely remove a utility

I'm thinking mixins would provide the best API from a usage point of view, similarly to what sass-mq does for adding breakpoints. allowing to only do:

@include utilities-add-values(...)

instead of having to assign the result of the function each time:

$utilities: utilities-add-values(...)

Motivation and context

The API for manipulating the $utilities map is well documented, but it relies on the low level map-merge. This makes it a bit of a mouthful to write the operations, especially for adding new values to existing utilities.

Start with the documented $utilities API in the Bootstrap utilities documentation and compare its low-level map-merge usage with the proposed operations. Review the existing Sass utilities configuration and determine how mixins or functions should add, replace, remove, and update utility options. Done means the supported operations are exposed through a clear API and documented with usage examples.