default favicon for a theme?

I am developing a theme and I wonder if there is a possibility to have a default favicon.

Details: The theme already has support for adding favicon and users can go to

admin->customize->site identity 

and select an image for favicon. Is possible that the theme shows a default favicon in case user still hasn’t got to it?

You have to change the defualt Site Icon using the Customizer API.

$wp_customize->add_setting( 'site_icon' , array(
    'default'     => YOUR_IMAGE_URL_HERE,
) );