防止openlayers在draw绘制状态按shift功能失效

new Draw({
        source: this.map.source,
        type: type,
        geometryFunction: geometryFunction,
        condition: () => {
          return true;
        },
        freehandCondition: () => {
          return false;
        }
      });

　　freehandCondition可以设置默认按键条件，返回false即按键shift失效

　　condition为false则绘制功能失效，为true生效