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/ui/class-tours.php

@@ -95,8 +95,8 @@ class Tours {
 					'ajaxurl' => wu_ajax_url(),
 					'nonce'   => wp_create_nonce('wu_tour_finished'),
 					'i18n'    => [
-						'next'   => __('Next', 'wp-ultimo'),
-						'finish' => __('Close', 'wp-ultimo'),
+						'next'   => __('Next', 'wp-multisite-waas'),
+						'finish' => __('Close', 'wp-multisite-waas'),
 					],
 				]
 			);