Prepare 0.12.0 Release

[jfaltermeier]

• move devcontainer to gke directory
• create changelog
• update versions
• update vsix

[jfaltermeier]

LGTM, just two minor nitpicks and the TODO in the Changelog

Thanks, I updated the version and the TODO (link will properly work after merging the helm chart, but this happens at the end in our process)