Constant CHANGE_LOG_HEADER

Source
const CHANGE_LOG_HEADER: &str = "# Changelog

<!--
This file is automatically generated by our release process.
DO NOT edit it directly.
If you want to add a change log entry for this package,
please create a new file in /changes.d/<pr-number>.toml
Refer to the [README.md](/changes.d/README.md) for more information.
-->

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]
";