add warning to router

Author: Archmonger

docs/src/reference/router.md

@@ -18,6 +18,13 @@ A Single Page Application URL router, which is a variant of [`reactpy-router`](h
 
 URL router that enables the ability to conditionally render other components based on the client's current URL `#!python path`.
 
+!!! warning "Pitfall"
+
+    All pages where this component exists must have the same, or more permissive exposure within Django's [URL patterns](https://docs.djangoproject.com/en/5.0/topics/http/urls/#example). You can think of this component as a secondary, client-side router. Django still handles the primary server-side routes.
+
+    We recommend creating a route with a wildcard `.*` to forward routes to ReactPy. For example...
+    `#!python re_path(r"^/router/.*$", my_reactpy_view)`
+
 === "components.py"
 
     ```python