allow user to drop documents on edit form

[Quentinchampenois]

:tophat: What? Why?

:pushpin: Related Issues

• Related to #?
• Fixes #?

:clipboard: Subtasks

• [x] Add CHANGELOG entry
• [ ] If there's a new public field, add it to GraphQL API
• [ ] Add documentation regarding the feature
• [ ] Add/modify seeds
• [ ] Add tests
• [ ] Another subtask

:camera: Screenshots (optional)

[Quentinchampenois]

Hi @paulinebessoles,

My bad I based my PR on alt/petition_merge rather than alt/petition. I will probably clause this PR and open a new one.