Adds spacer and nobreak in menu links

So; that extra markup is most of what this library does, rather than CSS ::after pseudocontent. The span wrapper prevents the link from breaking its line between the last word and the icon. But yes, sometimes themes need to style the icons to make the spacing match the text in menus, especially the icon width and height. This is the CSS provided by the library.

If you provide me a link I can take a look.

I just added a "text external link" to the Links & Resources menu dropdown in the main navigation for https://www.nonprofitdrupal.org.

There you can see the awkward spacing between the last and second-to-last words.

Yup it looks like your theme is inserting a gap between elements, so adding elements adds gaps:

.menu .primary-nav__menu-link > span {
  gap: 0.5rem;
}

This would fix it:

.menu .primary-nav__menu-link.link-purpose  > span {
  gap: 0;
}