Allow modifying display type of persistent-others

[fcjr]

The persistent dock options can be configured to look like folders, change sorting, and view orientation.

This PR allows you to set these values by passing an optional custom type:

system.defaults.dock.persistent-others = [
    "~/Documents"
    "~/Downloads/file.txt"
    {
      path = "~/Appications";
      displayas = "folder";
      showas = "fan";
      arrangement = "date-modified";
    }
  ];

[bew]

Hello o/
Could we have textual enums for the various values for the arrangement, showas, displayas ?
Or at the very least list the possible values and what they mean 🤔
Could you also explain how showas & displayas are different?

[fcjr]

Could we have textual enums for the various values for the arrangement, showas, displayas ? Or at the very least list the possible values and what they mean 🤔 Could you also explain how showas & displayas are different?

Sure, updated w/ slightly better comments and enums

[fcjr]

New to nix so not too sure how to fix the tests just yet, but continuing to poke around. If anyone has any suggestions lmk :)