Add and maintain a Changelog

[Weibye]

What problem does this solve or what need does it fill?

Based on this comment but generally having a changelog help users quickly get a high-level overview of the project and how it compares to its forks

What solution would you like?

• Create a Changelog.md in root and keep it up to date according to https://keepachangelog.com/en/1.0.0/
• Add a note in PR-template that user should update changelog if relevant
• All pull requests that contains a relevant change, should add single-line note of the change in the Changelog.md under the ## [Unreleased] section
• When cutting a release:
  1. Replace the header ## [Unreleased] with the date and version of the release: ## [x.y.z] - YYYY-MM-DD
  2. Add a new ## [Unreleased] header near the top of the document

What alternative(s) have you considered?

Keep as is and don't keep a changelog.

[alice-i-cecile]

This is done, as RELEASES.md :)

[Weibye]

Oh, right, thanks!