feat: nixvim refactor

modules/home-manager/programs/nixvim/presets/mergetool.nix

@@ -0,0 +1,22 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  cfg = config.presets.mergetool;
+in
+{
+  options.presets.mergetool = {
+    enable = lib.mkEnableOption "Mergetool";
+  };
+
+  config = lib.mkIf cfg.enable {
+    globals = {
+      mergetool_layout = "mr";
+      mergetool_prefer_revision = "local";
+    };
+    extraPlugins = [ pkgs.vimPlugins.vim-mergetool ];
+  };
+}