feat(nvim): enable nixd

configs/nixos/modules/shell/nvim/default.nix

@@ -32,6 +32,7 @@ in
           ripgrep # backs the picker's live grep
           fd # backs the picker's file finder
           wl-clipboard # provides a non-blocking clipboard provider on Wayland
+          nixd # provides Nix language-server support
         ];
 
         globals.mapleader = " ";
@@ -189,6 +190,8 @@ in
               installRustc = false;
               installRustfmt = false;
             };
+
+            servers.nixd.enable = true;
           };
 
           gitsigns = {