message: support disabled property in dropdown
diff: @@ -568,6 +568,7 @@ export class Dropdown extends DropdownMixin {
  type="button"
  id={this.props.id}
  aria-describedby={describedBy}
  + disabled={disabled}
  >
  <span className="pf-c-dropdown__toggle-text">
  {titlePrefix && `${titlePrefix}: `}
  