common: propose a new changelog format

CHANGELOG.md

+# 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/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+- Support Python 3.12 ([#391](https://github.com/stack-of-tasks/eigenpy/pull/391))
+
+### Fixed
+- Add method to `std::vector<MatrixXX>` binding even if another library had registered it ([#393](https://github.com/stack-of-tasks/eigenpy/pull/393))
+
+### Changed
+- CMake minimal version is now 3.10 ([#388](https://github.com/stack-of-tasks/eigenpy/pull/388))