Autofocus on username field

Useful UX improvement

views/site/login.php

@@ -24,7 +24,7 @@ $this->params['breadcrumbs'][] = $this->title;
         ],
     ]); ?>
 
-        <?= $form->field($model, 'username') ?>
+        <?= $form->field($model, 'username')->textInput(['autofocus' => 'autofocus']) ?>
 
         <?= $form->field($model, 'password')->passwordInput() ?>