docs: fix PHPDoc types in Route class.

system/Router/RouteCollectionInterface.php

@@ -31,7 +31,7 @@ interface RouteCollectionInterface
      * @param array|Closure|string $to
      * @param array                $options
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function add(string $from, $to, ?array $options = null);
 
@@ -46,31 +46,31 @@ public function add(string $from, $to, ?array $options = null);
      * @param array|string $placeholder
      * @param string       $pattern
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function addPlaceholder($placeholder, ?string $pattern = null);
 
     /**
      * Sets the default namespace to use for Controllers when no other
      * namespace has been specified.
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function setDefaultNamespace(string $value);
 
     /**
      * Sets the default controller to use when no other controller has been
      * specified.
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function setDefaultController(string $value);
 
     /**
      * Sets the default method to call on the controller when no other
      * method has been set in the route.
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function setDefaultMethod(string $value);
 
@@ -81,7 +81,7 @@ public function setDefaultMethod(string $value);
      * find words and meaning in the URI for better SEO. But it
      * doesn't work well with PHP method names....
      *
-     * @return mixed
+     * @return RouteCollectionInterface
      */
     public function setTranslateURIDashes(bool $value);