Release 13.11

> How to

During release

1. Push the new version which will create a Docker image with the stable version:

   bundle exec rake "release:single[X.Y]"

2. Edit content/_data/versions.yaml and rotate the versions.
3. Edit Dockerfile.master and rotate the versions.

Before merge

On the 22nd, before merging this MR:

1. Bump the dropdown versions for all online versions:

   bundle exec rake release:dropdowns

   This will create all the needed merge requests and will set them to MWPS.
2. Once all above MRs are merged, check the newly-created pipelines of the respective versions https://gitlab.com/gitlab-org/gitlab-docs/pipelines. Once they are green, it's time to merge this MR.
3. Manually run the "Build docker images weekly" scheduled pipeline. This is needed so that the image:docs-latest image is built that will contain all the updated versions.