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

views/legacy/signup/pricing-table/frequency-selector.php

@@ -28,9 +28,9 @@ if ( ! defined('ABSPATH')) {
 	<?php
 
 	$prices = [
-		1  => __('Monthly', 'wp-ultimo'),
-		3  => __('Quarterly', 'wp-ultimo'),
-		12 => __('Yearly', 'wp-ultimo'),
+		1  => __('Monthly', 'wp-multisite-waas'),
+		3  => __('Quarterly', 'wp-multisite-waas'),
+		12 => __('Yearly', 'wp-multisite-waas'),
 	];
 
 	$first = true;