add: autofocus login field on login page

        <div class="main">

          <div class="wrapper">

            {% call macros.render_form(form, action_url=url_for('login'), action_text='Login', class_='form-signin', btn_class='btn btn-info btn-lg btn-primary btn-block') %}

              {{ macros.render_field(form.username, placeholder='Username', type='text') }}

              {{ macros.render_field(form.username, placeholder='Username', type='text', autofocus=true) }}

              {{ macros.render_field(form.password, placeholder='Password', type='password') }}

              {{ macros.render_checkbox_field(form.remember) }}

            {% endcall %}