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.

flash(msg, "error")
        except Exception as e:
            flash("Error rendering template: " + str(e), "error")
        
        
        
        
        
        task = ti.task.unmap(None)
        title = "Rendered Template"
        html_dict = {}
        renderers = wwwutils.get_attr_renderer()
        for template_field in task.template_fields:
            content = getattr(task, template_field)
            renderer = task.template_fields_renderers.get(template_field, template_field)
            if renderer in renderers:
                if isinstance(content, (dict, list)):
                    json_content = json.dumps(content, sort_keys=True, indent=4)
                    html_dict[template_field] = renderers[renderer](json_content)
                else:
                    html_dict[template_field] = renderers[renderer](content)
            else:
                html_dict[template_field] = Markup("<pre><code>{}</pre></code>").format(pformat(content))
            if isinstance(content, dict):
                if template_field == "op_kwargs":
                    for key, value in content.items():
                        renderer = task.template_fields_renderers.get(key, key)
                        if renderer in renderers:
                            html_dict[".".join([template_field, key])] = renderers[renderer](value)
                        else: