Prep Plugin for release on WordPress.org (#23)

* Update translation text domain
* Escape everything that should be escaped.
* Add nonce checks where needed.
* Sanitize all inputs.
* Apply Code style changes across the codebase.
* Correct many deprecation notices.
* Optimize load order of many filters.
* Add Proper Build script
* Use emojii flags
* Fix i18n deprecation  notice for translating too early
* Put all scripts in footer and load async

inc/admin-pages/class-customizer-admin-page.php

@@ -89,7 +89,16 @@ abstract class Customizer_Admin_Page extends Edit_Admin_Page {
 
 		parent::register_scripts();
 
-		wp_enqueue_script('wu-customizer', wu_get_asset('customizer.js', 'js'), ['jquery', 'wu-vue', 'wu-block-ui']);
+		wp_enqueue_script(
+			'wu-customizer',
+			wu_get_asset('customizer.js', 'js'),
+			['jquery', 'wu-vue', 'wu-block-ui'],
+			\WP_Ultimo::VERSION,
+			[
+				'async'     => true,
+				'in_footer' => true,
+			]
+		);
 
 		wp_enqueue_style('wp-color-picker');