Add Iconnoir icons, handle icons names starting with digits

[smee]

[tatut]

heroicons looks empty in the diff

[smee]

Ok, this turns out to be more complicated than I initially thought: heroicons now have different paths for the solid/outline icons, but their filenames are identical. So regenerating heroicons means that one variant overwrites the other. I would suggest, I don't regenerate the other icons and only add the Iconoir icons. Do you agree?

[tatut]

Yes, sounds reasonable. Just add the new ones.