SubMenu doesn't actually support itemIcon like docs suggest

[alibosworth]

in SubMenu.jsx, "itemIcon" is defined as a prop, however only expandIcon is actually rendered:

   // expand custom icon should NOT be displayed in menu with horizontal mode.
    let icon = null;
    if (props.mode !== 'horizontal') {
      icon = this.props.expandIcon; // ReactNode
      if (typeof this.props.expandIcon === 'function') {
        icon = React.createElement(
          this.props.expandIcon,
          { ...this.props }
        );
      }
    }

    const title = (
      <div
        ref={this.saveSubMenuTitle}
        style={style}
        className={`${prefixCls}-title`}
        {...titleMouseEvents}
        {...titleClickEvents}
        aria-expanded={isOpen}
        {...ariaOwns}
        aria-haspopup="true"
        title={typeof props.title === 'string' ? props.title : undefined}
      >
        {props.title}
        {icon || <i className={`${prefixCls}-arrow`} />}
      </div>
    );

[Michael101sh]

@picodoth @yiminghe @afc163 @zombieJ Can you please fix it?

[zombieJ]

icon prop added 4.2.0. Pls use this instead:

https://ant.design/components/menu/#Menu.SubMenu