Fix typo in method name of main Server class.

Author: Potherca

src/Server.php

@@ -45,7 +45,7 @@ final public function respondToAccessTokenRequest(Request $request) : Response
         }
     }
 
-    final public function respondToWellKnowRequest() : Response
+    final public function respondToWellKnownRequest() : Response
     {
         $response = $this->response;