dummy plugin

<?php
namespace Elementor;

class My_Widget extends Widget_Base {

    public function __construct() {
        parent::__construct(
            'my-widget',
            __('My Widget', 'text-domain'),
            array(
                'description' => __('A simple widget', 'text-domain'),
                'categories' => array('general'),
                'icon' => 'fa fa-bell',
            )
        );
    }

    public function get_render_template() {
        return plugin_dir_path(__FILE__) . 'my-widget-template.php';
    }

    public function _content_template() {
        ?>
        <div class="my-widget">
            <h3>{{{ settings.title }}}</h3>
            <p>{{{ settings.content }}}</p>
        </div>
        <?php
    }

    protected function _register_controls() {
        $this->start_controls_section(
            'section_content',
            array(
                'label' => __('Content', 'text-domain'),
            )
        );

        $this->add_control(
            'title',
            array(
                'label' => __('Title', 'text-domain'),
                'type' => Controls_Manager::TEXT,
                'default' => __('My Widget Title', 'text-domain'),
                'placeholder' => __('Enter title', 'text-domain'),
            )
        );

        $this->add_control(
            'content',
            array(
                'label' => __('Content', 'text-domain'),
                'type' => Controls_Manager::TEXTAREA,
                'default' => __('My Widget Content', 'text-domain'),
                'placeholder' => __('Enter content', 'text-domain'),
            )
        );

        $this->end_controls_section();
    }

    protected function render() {
        $settings = $this->get_settings_for_display();
        $this->add_render_attribute('wrapper', 'class', 'my-widget');
        ?>
        <div <?php echo $this->get_render_attribute_string('wrapper'); ?>>
            <h3><?php echo $settings['title']; ?></h3>
            <p><?php echo $settings['content']; ?></p>
        </div>
        <?php
    }
}

Plugin::instance()->widgets_manager->register_widget_type( new My_Widget() );