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/class-session-cookie.php

@@ -137,7 +137,7 @@ class Session_Cookie implements Session {
 			$expire = HOUR_IN_SECONDS;
 		}
 
-		$value = json_encode($this->data, JSON_UNESCAPED_UNICODE);
+		$value = wp_json_encode($this->data, JSON_UNESCAPED_UNICODE);
 
 		$cookie = new Cookie($this->get_cookie_name());
 		$cookie->setValue($value);