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/duplication/functions.php

@@ -75,7 +75,7 @@ if ( ! class_exists('MUCD_Functions') ) {
 				return true;
 			}
 
-            return get_blog_option($blog_id, 'mucd_duplicable', 'no') == 'yes';
+			return get_blog_option($blog_id, 'mucd_duplicable', 'no') == 'yes';
 		}
 
 		/**