Update changelog

Author: epiphone

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [1.8.1] - 2020-04-10
+### Fixed
+- Restored the mistakenly removed `tslib` dependency [#42](https://github.com/epiphone/routing-controllers-openapi/issues/42)
+
 ## [1.8.0]
 ### Added
 - Upgraded dependencies, now supporting `routing-controllers@^0.8.0` ([#33](https://github.com/epiphone/routing-controllers-openapi/issues/33))