Update tested Wordpress versions

Author: chrislarrycarl

README.md

@@ -13,11 +13,11 @@ To download just the plugin (without the developer extras in this repo) check ou
 
 ### Compatibility
 
-[![WordPress Compatibility](https://img.shields.io/badge/WordPress-4.7_to_5.7-blue.svg?logo=wordpress)](https://wordpress.org/) [![PHP Compatibility](https://img.shields.io/badge/PHP-5.6_to_7.4-%238892BF.svg?logo=php)](https://php.net/)
+[![WordPress Compatibility](https://img.shields.io/badge/WordPress-4.7_to_5.8-blue.svg?logo=wordpress)](https://wordpress.org/) [![PHP Compatibility](https://img.shields.io/badge/PHP-5.6_to_7.4-%238892BF.svg?logo=php)](https://php.net/)
 
 utm.codes is developed for, and tested with, a variety of recent platform versions, including:
 
-- WordPress 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, and 5.7
+- WordPress 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, and 5.8
 - PHP 5.6, 7.0, 7.1, 7.2, 7.3, and 7.4
 
 ## Branches