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.

table = [
                (section, key, str(value), source)
                for section, parameters in conf.as_dict(True, display_sensitive).items()
                for key, (value, source) in parameters.items()
            ]
            return self.render_template(
                template="airflow/config.html",
                title=title,
                table=table,
            )
        else:
            return self.render_template(
                "airflow/config.html",
                title=title,
                hide_config_msg=(
                    "Your Airflow administrator chose not to expose the configuration, "
                    "most likely for security reasons."
                ),
            )
class RedocView(AirflowBaseView):
    """Redoc Open API documentation."""
    default_view = "redoc"
    @expose("/redoc")
    def redoc(self):
        """Redoc API documentation."""
        openapi_spec_url = url_for("/api/v1./api/v1_openapi_yaml")
        return self.render_template("airflow/redoc.html", openapi_spec_url=openapi_spec_url)
class DagFilter(BaseFilter):
    """Filter using DagIDs."""
    def apply(self, query, func):