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.

"""Get Execution Data, Base Date & Number of runs from a Request."""
    date_time = www_request.args.get("execution_date")
    run_id = www_request.args.get("run_id")
    
    if run_id:
        dagrun = dag.get_dagrun(run_id=run_id, session=session)
        date_time = dagrun.execution_date
    elif date_time:
        date_time = _safe_parse_datetime(date_time)
    else:
        date_time = dag.get_latest_execution_date(session=session) or timezone.utcnow()
    base_date = www_request.args.get("base_date")
    if base_date:
        base_date = _safe_parse_datetime(base_date)
    else:
        
        
        base_date = (date_time + datetime.timedelta(seconds=1)).replace(microsecond=0)
    default_dag_run = conf.getint("webserver", "default_dag_run_display_number")
    num_runs = www_request.args.get("num_runs", default=default_dag_run, type=int)