chore(style): add styling for back button
chore(style): add styling for back button

related to CAM-4776

xlinur/camunda-bpm-webapp,tcrossland/camunda-bpm-webapp,xlinur/camunda-bpm-webapp,TitanUser/camunda-bpm-webapp,TitanUser/camunda-bpm-webapp,tcrossland/camunda-bpm-webapp,TitanUser/camunda-bpm-webapp,tcrossland/camunda-bpm-webapp,xlinur/camunda-bpm-webapp