[skip ci] Added Update instructions to change log.

Author: Chris Wiechmann

CHANGELOG.md

@@ -12,6 +12,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - ILM policies optimized for the ideal index sizes [#68](https://github.com/Axway-API-Management-Plus/apigateway-openlogging-elk/issues/68)
 
+### Added
+- Initial version of Update instructions. See [UPDATE.md](UPDATE.md)
+
 ## [2.0.1] 2021-01-28
 ### Fixed
 - Avoid a Race-Condition by making the variable apiProxy locally instead of global [#61](https://github.com/Axway-API-Management-Plus/apigateway-openlogging-elk/issues/61)