Support for Nextcloud Projects (Related Resources? Tags?)

### Is your feature request related to a problem? Please describe.
The Web UI allows users to create relationships between files, deck cards, talk rooms etc.
The Android app does not allow this.

### Describe the solution you'd like
A first step for feature parity would be to display readonly existing projects and allow to open linked stuff.
In a second step it would be awesome to allow adding files to existing projects.
In a third step one could allow creating new projects starting from a file.

### Describe alternatives you've considered
No feature parity at all 🤷

### Additional context
The Deck Android app already displays Projects (readonly) and plans to extend the support to write access in the future.