thunar: improvements (close #10306)
Add the possibility to specify plugin set to
be used as overridable `thunar` derivation argument.
New nixos config attribute:
`services.xserver.desktopManager.xfce.thunarPlugins`
that allows user to specify plugins in the context
of nixos.
Tests:
- With and without plugins.
- Using the nixos attributes.
authored by Raymond Gauthier and committed by Vladimír Čunát 662bbb52 b2409581