Utilities map configuration functions

Created by: romaricpascal

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.