[Feature]: Custom fields support

[QazCetelic]

Description

The Paperless web interface has a feature to add custom fields to documents:

Screenshot

These are then visible when viewing the document:

Screenshot

It would be nice to also be able to view and edit these with this app.

I could take a look to see if I can implement it myself, but I have very limited experience with Flutter. I did try to clone the project, but I got 13525 compile errors which I don't know how to solve.

[astubenbord]

Hi, it already works in my current development state. However, I have quite a lot of changes there, so it might still take a while until I can publish a new update. Unfortunately I don't have that much spare time to work on this project at the moment, but there's light at the end of the tunnel, so hopefully I'll get to work on this more frequently in the upcoming weeks!