A site editor can add icons to menu item links (after enabling a submodule)

Problem/Motivation

We would like to allow site managers and content editors to choose icons to associate with links in their menus.

Steps to reproduce

Proposed resolution

Add a submodule that works a bit like https://www.drupal.org/project/menu_link_attributes → or https://www.drupal.org/project/simple_menu_icons → but would allow selecting from the theme-defined icons rather than allowing free-text attributes or uploading an icon; it would then display the icon with the menu item or provide instructions for modifying templates so this will work. Would a pull request be accepted with this feature?

Remaining tasks

User interface changes

API changes

Data model changes