The DAGs main page has All/Active/Paused.

It would be nice if we can have also Running Now which will show all the DAGs that have at least 1 in Running of DAG runs:
![Screen Shot 2021-08-25 at 11 30 55](https://user-images.githubusercontent.com/62940116/130756490-647dc664-7528-4eb7-b4d8-515577f7e6bb.png)


For the above example the new DAGs tab of Running Now should show only 2 rows.
The use case is to see easily what DAGs are currently in progress.

task_dict["run_id"] = dag_run_id
            tasks.append(task_dict)
        task_names = [ti.task_id for ti in tis]
        data = {
            "taskNames": task_names,
            "tasks": tasks,
            "height": len(task_names) * 25 + 25,
        }
        session.commit()
        return self.render_template(
            "airflow/gantt.html",
            dag=dag,
            dag_run_id=dag_run_id,
            execution_date=dttm.isoformat(),
            form=form,
            data=data,
            base_date="",
            root=root,
            dag_model=dag_model,
        )
    @expose("/extra_links")
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    @provide_session
    def extra_links(self, *, session: Session = NEW_SESSION):