Add event link is broken in template

Problem/Motivation

Add event link returns 404 error in console:

An AJAX HTTP error occurred.
HTTP Result Code: 404
Debugging information follows.
Path: fullcalendar-view-event-add?entity=node&bundle=event&start_field=field_event_dates&end_field=field_event_dates&destination=/manage/events
StatusText: Not Found
ResponseText: The website encountered an unexpected error. Please try again later.Symfony\Component\HttpKernel\Exception\NotFoundHttpException: No route found for "POST /manage/fullcalendar-view-event-add" ....

Template add event url needs to be fixed to match Add event route.

Steps to reproduce

Create new Fullcalendar view page.
Check "Create a new event via the Off-Canvas dialog." under view Settings => Display.
Go to the view page and check Add event link under the calendar.

Proposed resolution

Added patch with template fix.