feat: add closed issues csv export

This MR adds a page that lets you export all closed issue from a certain date. From time to time developers in the DA team were tasked to manually export such list, where this MR will allow delivery manager to export this list themselves whenever they need to. Hopefully this will be useful for other teams as well.

I realise that this is a very specific task, and if we were to include all of these specific tasks in this application, it might become a bit of a mess. I am therefore open to any suggestions how we could structure this so that it's still available, but maybe not cluttering other useful utilities in this application.