Attachments for newsletters

[Pi2048]

In the documentation, it says that newsletters can contain attachments. See https://github.com/jonge-democraten/website/blame/master/docs/user.md#L220.

When I try to create a newsletter, I do not see a field to enter attachments.

We should a) implemnet this functionality and b) fix the documentation until then.

[trolando]

Please remind me, was the outcome of the internal discussion that attachments should be supported? In that case I suppose I could remove the blocks...