Update CHANGELOG about readonly property

Author: zonuexe

CHANGELOG.md

@@ -8,6 +8,7 @@ All notable changes of the PHP Mode 1.19.1 release series are documented in this
 
  * Support new PHP 8.0 and 8.1 syntax hilighting and indentation
     * [8.0] `#[Attributes]`
+    * [8.1] `readonly` property ([#680])
  * Add `php-imenu-generic-expression-default` for default value or `php-imenu-generic-expression`
    * Add `php-imenu-generic-expression-legacy` for compatibility
    * Add `php-imenu-generic-expression-simple` for simple display
@@ -27,6 +28,7 @@ All notable changes of the PHP Mode 1.19.1 release series are documented in this
    * Unified `Classes`, `Traits`, `Interfaces` into `Classes`
 
 [#669]: https://github.com/emacs-php/php-mode/pull/669
+[#680]: https://github.com/emacs-php/php-mode/pull/680
 
 ## [1.24.0] - 2021-03-07