Package diff link in releases is wrong

[tomuben]

The link to package diffs in our release is wrong, because it contains the relative link.
See https://github.com/exasol/script-languages-release/blob/master/doc/changes/changes_10.0.0.md#package-version-comparison-between-release-1000-and-970

The Readme.md is just copied during the release from the doc/changes to the release notes -> The relative link does not work.

There are two options:

• Modify the Readme.md during the Github release creation and replace the relative link with a link to the master branch
• Investigate Github autolinks if they could resolve this issue