Prepare release 0.9.1 - Githubissues

[x] Is the title of the Pull Request correct?
[ ] Is the title of the corresponding issue correct?
[x] Have you updated the changelog?
[x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
[ ] Are you mentioning the issue which this PullRequest fixes ("Fixes...")
[x] Before you merge don't forget to run tests in AWS CodeBuild, by adding [CodeBuild] to the commit message Fixes missed version number update, no issue

exasol / transformers-extension