Add theme support for the Customizer Image Control

Just enqueue the JavaScript-file from the plugin to the Customizer (Issue #90)

// Add Global Media Gallery JS to Customize.php
function add_multisite_global_media_to_customizer() {
    wp_register_script(
        'multisite_global_media',
        '/wp-content/plugins/multisite-global-media/assets/js/global-media.js',
        ['jquery'],
        '1.1',
        true
    );
    wp_enqueue_script( 'multisite_global_media' );
}
add_action( 'customize_controls_print_footer_scripts', 'add_multisite_global_media_to_customizer' );