Keep a changelog in the repo

[tfr42]

Besides the generated change logs per release a changelog file in mark down shall be kept in the repo.

https://keepachangelog.com/en/1.0.0/

[tfr42]

The TMC would like to have such change log but would like to avoid any additional manual labor to maintain it.

[stephanr]

In addition it would also be nice to have explicit links in README.md and/or the Website to point to the actual Releases page on github.
It may would also make sense to create a separate CHANGELOG.md that also references the github relases page as well.