How to create a widget that accepts html input?

Thanks to @TomJNowell for his advise on using textarea.

This is what I did to achieve what I wanted. It serves the purpose but I am not sure if it is the right way or not.

• I changed below input field:

        <p>
            <label for="<?php echo $this->get_field_id('headline'); ?>">Headline</label><br />
            <input type="text" name="<?php echo $this->get_field_name('headline'); ?>" id="<?php echo $this->get_field_id('headline'); ?>" value="<?php echo $instance['headline']; ?>" class="widefat" />
        </p>

To a textarea:

        <p>
            <label for="<?php echo $this->get_field_id('headline'); ?>">Headline</label><br />
            <textarea name="<?php echo $this->get_field_name('headline'); ?>" id="<?php echo $this->get_field_id('headline'); ?>" class="widefat" rows="5"><?php echo $instance['headline']; ?></textarea>
        </p>

And this is my update function:

    public function update( $new_instance, $old_instance ) {
        // processes widget options to be saved
        $instance = $old_instance;
        $instance['headline']   =   wp_kses_post($new_instance['headline']);
        $instance['description'] = strip_tags( $new_instance['description'] );
        $instance['link_title'] = strip_tags( $new_instance['link_title'] );
        $instance['link_url'] = strip_tags( $new_instance['link_url'] );
        $instance['image_uri'] = strip_tags( $new_instance['image_uri'] );
        return $instance;       
    }