Fix CORS when sign up

diskuy_back/lib/diskuy_web/router.ex

@@ -32,6 +32,7 @@ defmodule DiskuyWeb.Router do
     options   "/post", PostController, :options
     options   "/post/:id", PostController, :options
     post "/users/signup", UserController, :create
+    options   "/users/signup", PostController, :options
     post "/users/signin", UserController, :signin
   end