adding css to make expand collapse presentation as per wcms2

css/styles.css

source/_patterns/00-config/01-mixins/_mixins.button.scss

source/_patterns/02-base/00-fonts/_fonts.scss

source/_patterns/04-components/button/_button.scss

source/_patterns/04-components/button/button.twig

...terns/04-components/expand-collapse/_expand-collapse.scss

...atterns/04-components/expand-collapse/expand-collapse.yml