I built a custom widget and hosted it on portal. Created a Web App Builder application with Billboard theme in portal and added my custom widget along with 4 other out of box widgets. This Web app builder is now added to Dashboard along with Survey form and ListView. Now I would like to change ".jimu-widget-onscreen-icon" and ".jimu-widget-onscreen-iconimg" to reduce icon sizes in the Web app builder. What is the right approach?