update changelog before release v0.3.1

Author: francesco086

CHANGELOG.md

@@ -1,4 +1,5 @@
 # Changelog
+
 All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
@@ -9,11 +10,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Anything MAY change at any time. The public API SHOULD NOT be considered stable.").
 While in this phase, we will denote breaking changes with a minor increase.
 
+## 0.3.1
+
+### Changed
+
+* Update code to be compatible with pydantic v2 (no retro-compatibility with v1)
 
 ## 0.3.0
+
 ### Changed
+
 * Dependencies passed in CLI `--pkg-dependencies` or `PyProjectConfig` must be separated by `;` or newline (previously was `,` or newline)
 
 ## 0.2.0
+
 ### Added
+
 * First release of `dac`