[Icons] Add documentation on icons colors#3082

Kocal merged 1 commit intosymfony:2.xsymfony/ux:2.xfrom

StevenRenaux:Fix/Fix-icon-color-fill-and-stroke-attributesStevenRenaux/ux:Fix/Fix-icon-color-fill-and-stroke-attributesCopy head branch name to clipboard