Attachments drop file

[brendanlaschke]

Scope & Context

Attachments allow for a file upload - do we want the ability to drop a file onto the attachments tab @Bonapara?

Current behavior

We can add files only via the button.

Expected behavior

Drop a file to upload it.

[FelixMalfait]

This would be very cool! I added "design needed" for the drop area (when you're hover it but haven't released it yet), but we can start with something very basic

[Bonapara]

Replaced by #3345