Fix emacs config.

nix/configuration/roles/emacs/files/emacs/elisp/lang-xml.el

@@ -0,0 +1,17 @@
+(defun xml-fmt ()
+  "Run xmllint --format."
+  (run-command-on-buffer "xmllint" "--format" "-")
+  )
+
+(use-package nxml-mode
+  :commands (nxml-mode)
+  :pin manual
+  :ensure nil
+  :hook (
+         (nxml-mode . (lambda ()
+                        (add-hook 'before-save-hook 'xml-fmt nil 'local)
+                        ))
+         )
+  )
+
+(provide 'lang-xml)