"!" characters in Worksheet title will make reference formulas crash PHPOffice#325

 add information to changelog

Author: bayzhanov

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Sheet title can contain exclamation mark - [#325](https://github.com/PHPOffice/PhpSpreadsheet/issues/325)
 - Allow iterators to go out of bounds with prev - [#587](https://github.com/PHPOffice/PhpSpreadsheet/issues/587)
 - Fix warning when reading xlsx without styles - [#631](https://github.com/PHPOffice/PhpSpreadsheet/pull/631)