/* CSS in menu-icon.css */
#toplevel_page_campaigner-settings .wp-menu-image:before {
    background-image: url("../images/campaigner-favicon.svg") !important;
    height: 3px !important;
    width: 22px !important;
    float: left !important;
    margin-top: 10px !important;
    margin-left: 6px !important;
    background-repeat: no-repeat;
    content: '' !important;
    background-size: contain;
}