techdocs: fix addons not rendering on subpages with react router v6

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/moody-berries-sneeze.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs': patch
+---
+
+Fixed a bug where addons wouldn't render on sub pages when using React Route v6 stable.

plugins/techdocs/src/Router.tsx

@@ -68,7 +68,7 @@ export const EmbeddedDocsRouter = (props: PropsWithChildren<{}>) => {
       element: <EntityPageDocs entity={entity} />,
       children: [
         {
-          path: '/*',
+          path: '*',
           element: children,
         },
       ],