add rel attribute to button shortcode

layouts/shortcodes/button.html

@@ -2,6 +2,7 @@
   class="!rounded-md bg-primary-600 px-4 py-2 !text-neutral !no-underline hover:!bg-primary-500 dark:bg-primary-800 dark:hover:!bg-primary-700"
   {{ with .Get "href" }}href="{{ . }}"{{ end }}
   {{ with .Get "target" }}target="{{ . }}"{{ end }}
+  {{ with .Get "rel" }}rel="{{ . }}"{{ end }}
   role="button"
 >
   {{ .Inner }}