feat: Niri additions

- Switch to unstable branch.
- Run xwayland-sattelite as a serivce.
- Initialise terminal windows at smaller widths.
- Style & bind tabs.
- Block out private windows.
- Binds for dynamic casting.

modules/nixos/niri.nix

@@ -8,10 +8,13 @@ in {
 
   config = lib.mkIf cfg.enable {
     nixpkgs.overlays = [ inputs.niri.overlays.niri ];
+
     programs.niri = {
       enable = true;
       package = pkgs.niri-unstable;
     };
+
+    security.pam.services.swaylock = {};
     
     # Necessary for e.g. screensharing.
     xdg.portal = {