Add neovim config using nixvim

programs/nixvim/default.nix

@@ -0,0 +1,21 @@
+{ pkgs, ... }:
+
+{
+  imports = [
+    ./options.nix
+    ./keymappings.nix
+    ./completion.nix
+    ./_plugins
+  ];
+
+  programs.nixvim = {
+    enable = true;
+
+    defaultEditor = true;
+
+    nixpkgs.useGlobalPackages = true;
+
+    viAlias = true;
+    vimAlias = true;
+  };
+}