BARN-63: update readme

Author: cgaroutte

CHANGELOG.md

@@ -5,7 +5,7 @@ Inspired by [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 Note: This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [2.1.0] - UNRELEASED
-### Changed
+### Added
 - Added optional `parameter_start` and `parameter_end` arguments for the following methods:
   - `ParameterSubstitution.find_tokens`
   - `ParameterSubstitution.find_formatters`