Allow cards to contain files

[Mr-Personality]

This is extremely ambitious and I don't expect this to be implemented, but it would be great if you could paste or drag Windows files into cards, and then that file is "moved" into that card.

The file(s) then appear at the foot of each card and function like windows icons, so you can rename them, open them, or cut and paste them.

All the files contained within Kanbanion would be moved into a special directory, with sub-folders for each card.

This feature would be extremely useful to me, as I often have tons of important files on my desktop that I'm currently working on. If I could tidy them all into job cards, it would be fantastic!

[nmaggioni]

This would require a significant refactor of the storage format, as well as paying special attention to the cross-platform way of handling files. For the moment I think that this is a task for which you shouldn't rely on a lightweight Electron application - given #9, I'd suppose that a proper folder structure could better suit your use case:

• My Projects
  • Project 1
    • Files
      • file1.ext
      • file2.ext
    • kanbanion.json
  • Project 2
    • Files
      • file3.ext
    • kanbanion.json