docs: add typehint to controller methods

Author: kenjis

user_guide_src/source/tutorial/news_section/003.php

@@ -13,7 +13,7 @@ public function index()
         $data['news_list'] = $model->getNews();
     }
 
-    public function show($slug = null)
+    public function show(?string $slug = null)
     {
         $model = model(NewsModel::class);
 

user_guide_src/source/tutorial/news_section/006.php

@@ -9,7 +9,7 @@ class News extends BaseController
 {
     // ...
 
-    public function show($slug = null)
+    public function show(?string $slug = null)
     {
         $model = model(NewsModel::class);
 

user_guide_src/source/tutorial/static_pages/001.php

@@ -9,7 +9,7 @@ public function index()
         return view('welcome_message');
     }
 
-    public function view($page = 'home')
+    public function view(string $page = 'home')
     {
         // ...
     }

user_guide_src/source/tutorial/static_pages/002.php

@@ -8,7 +8,7 @@ class Pages extends BaseController
 {
     // ...
 
-    public function view($page = 'home')
+    public function view(string $page = 'home')
     {
         if (! is_file(APPPATH . 'Views/pages/' . $page . '.php')) {
             // Whoops, we don't have a page for that!