Create "only load selected icons" functionality

Problem/Motivation

Currently when loading the default bootstrap icons from the module, every icon gets loaded and raises a "Excessive DOM size" error in lighthouse.

Steps to reproduce

Load the default bootstrap ui kit iconset and view any page on the FE.

Proposed resolution

We should be some sort of functionality that allows the user to add the icon (maybe via an AJAX click when viewing the UI Kit), it could then update some config in the backend, then the user can split this if necessary (ie. multisite use with domain module installed). Afterwards we can save on performance and DOM size by only loading the selected icons into the svg sprite.

Remaining tasks

See above.

User interface changes

Some sort of "Add +" functionality.

API changes

N/A

Data model changes

TBD