lumo: allow importing of specific utility groups [V20]

[knoobie]

pre-requirement: vaadin/vaadin-lumo-styles#103

Currently all lumo utilities are inside a single file. It would be good to group the utilities by e.g. coloring, sizing, spacing, grid, flex or other and create separate files for each of them. Those groups can then be important depending on the developers need or just include lumo-all.css which includes @imports to each of the group the utilities.

This would allow for easier addition of new "groups" as well without forcing them onto the developer.

[anezthes]

Fixed in anezthes/lumo-css-framework@de67313.

[web-padawan]

Blocked by vaadin/flow#9794

[anezthes]

all-classes.css provided as a workaround.
https://github.com/anezthes/lumo-css-framework/blob/master/all-classes.css

[web-padawan]

Starting from Vaadin 21, it is now possible to import separate files from the utilities folder. Closing.