Add index page to the sidebar when it's the only page

Automatically include the index page in the documentation sidebar when it is the only page present. This ensures the sidebar is not empty for a single-page documentation site, providing a more user-friendly experience.

packages/framework/src/Framework/Features/Navigation/DocumentationSidebar.php

@@ -22,6 +22,11 @@ protected function generate(): void
                 $this->items->put($route->getRouteKey(), NavItem::fromRoute($route));
             }
         });
+
+        // If there are no pages other than the index page, we add it to the sidebar so that it's not empty
+        if($this->items->count() === 0 && DocumentationPage::home() !== null) {
+            $this->items->push(NavItem::fromRoute(DocumentationPage::home()));
+        }
     }
 
     public function hasGroups(): bool