Allow attach file to form

[supernovae]

Nextcloud (please complete the following information):

• Nextcloud-Version: [29.0.5]
• Forms-Version: [4.2.4]

Is your feature request related to a problem? Please describe.
I would like the ability to allow someone to attach a file - in this specific case, a screenshot or image - but any file type that could be saved would be nice.

Describe the solution you'd like
Add a new form field for file upload/attachment.

Describe alternatives you've considered
Right now I have people upload in their repo and then copy and paste a link as text file, it's not very pretty. I would like files to remain with form rather than potentially disappear as users manage their own storage.

Additional context
Allow attaching of a file to a form submission. Perhaps configurable as to file extension or types supported and max size for form.

[Chartman123]

Duplicate of #42