We should create mediawiki images that are based off the regularly released branches.
This should consist of:
* Reusing the needed parts from the mediawiki Dockerfile (see: https://github.com/wikimedia/mediawiki-docker/blob/7fb7a88b3dd745fdd1115ad701a1e5f5c6236420/1.35/apache/Dockerfile)
* Being based of the wmf weekly release branches
The built docker image should be available to the rest of the pipeline. This could mean either keeping the tar-ed image as an artefact. Or it could be uploading it to some docker registry somewhere. Options include ghcr.io and hub.docker.com.
Acceptance criteria:
[] Mediawiki Docker image built based off defined wmf weekly release branch is stored in a location that is accessible by Wikibase release pipeline
[] Wikibase release pipeline uses the specified version of Mediawiki docker image instead of hardcoded version 1.35