Spike: Allowing pasting of image content in markdown editor

[techsmyth]

Description

As a user I want to be able to cut and paste images into my markdown content, without having to save the image first to disk

Acceptance criteria

• [ ] Allow pasting of image content directly into markdown editor, with an upload to the relevant storage bucket happening in the background

Spike: half a day

Additional context

Presumably we can do this by first saving the pasted content to disk and then in the background do an image upload?