docs: Add example to toast_header()

Author: gadenbuie

shiny/ui/_toast.py

@@ -337,7 +337,7 @@ def tagify(self, closable: bool = False) -> Tag:
 
         return div({"class": "toast-header"}, *contents, **self.attribs)
 
-
+@add_example("toast")
 def toast_header(
     title: TagChild,
     *args: TagChild | TagAttrs,