DS-2906 by maikelkoopman: make navbar colors configurable and move colors to css file

assets/css/brand.css

assets/css/button.css

assets/css/cards.css

assets/css/datepicker.css

assets/css/hero.css

assets/css/navbar.css

assets/css/timepicker.css

color/color.inc

color/preview.html

components/00-config/mixins/_breakpoints.scss

components/00-config/variables/_alert.scss

components/00-config/variables/_buttons.scss

components/00-config/variables/_cards.scss

components/00-config/variables/_dropdown.scss

components/00-config/variables/_navbar.scss

components/03-molecules/navigation/navbar/navbar.scss

components/04-organisms/hero/hero.scss

components/brand.scss

config/install/socialblue.settings.yml

socialblue.libraries.yml