Allow multiple attachments to be uploaded when editing a previously created item

[idelsink]

What is the problem you are trying to solve with this feature?

Currently, you can upload multiple pictures when creating an item (see #528) but not when editing an existing item.

What is the solution you are proposing?

A similar solution like #528 but for editing items

What alternatives have you considered?

Additional context

I'm running Version: v0.18.0 ~ Build: 3a32804

Contributions

• I have searched through existing issues and feature requests to see if my idea has already been proposed.
• If this feature is accepted, I would be willing to help implement and maintain this feature.
• If this feature is accepted, I'm willing to sponsor the development of this feature.

[tankerkiller125]

Please note we're converting this issue into a discussion as per our new procedures/policies. You can read more about that in our announcement #712