Update CHANGELOG.md

Author: driesvints

CHANGELOG.md

@@ -1,6 +1,12 @@
 # Release Notes
 
-## [Unreleased](https://github.com/laravel/laravel/compare/v8.5.17...8.x)
+## [Unreleased](https://github.com/laravel/laravel/compare/v8.5.18...8.x)
+
+
+## [v8.5.18 (2021-05-18)](https://github.com/laravel/laravel/compare/v8.5.17...v8.5.18)
+
+### Changed
+- Add Octane cache store ([#5610](https://github.com/laravel/laravel/pull/5610), [637c85d](https://github.com/laravel/laravel/commit/637c85d624bf19355025b68aaa90e6cadf8a2881))
 
 
 ## [v8.5.17 (2021-05-11)](https://github.com/laravel/laravel/compare/v8.5.16...v8.5.17)