feat(jj): configure to use hunk.nvim if available

This should keep me inside of nvim for longer c:

modules/hm/dev.nix

@@ -123,9 +123,21 @@ in
             # Jujutsu (alternative DVCS (git-compatible))
             jujutsu = {
               enable = true;
+              # Use the more up to date version of jj
               package = pkgs.unstable.jujutsu;
               settings = {
-                ui.pager = "bat";
+                ui = lib.mkMerge [
+                  # If `bat` is available use it as the pager
+                  (lib.mkIf config.programs.bat.enable { pager = "bat"; })
+                  # if hunk.nvim is enabled use it as a diff editor
+                  (lib.mkIf config.programs.nixvim.plugins.hunk.enable {
+                    diff-editor = [
+                      "nvim"
+                      "-c"
+                      "DiffEditor $left $right $output"
+                    ];
+                  })
+                ];
                 fix.tools = builtins.mapAttrs (tool: cmd: jjFormatters.${tool} cmd) nvimFormatters;
                 # mimic git commit --verbose by adding a diff
                 templates.draft_commit_description = ''