Provide option to use yarn without zero-install method

According to https://gitlab.com/to-be-continuous/node/-/blob/master/templates/gitlab-ci-node.yml?ref_type=heads#L640 the --immutable-cache option gets passed to yarn for every job.

The option makes yarn fail, when the cache would be modified (either because files would be added, or because they'd be removed). See https://yarnpkg.com/cli/install#details

For me this seems, as if i am forced to use zero installs with yarn and therefore commit the node_modules to git. https://yarnpkg.com/features/caching#zero-installs

I would be happy if there is another way instead of zero installs. Currently I see two options:

• create a dedicated job to setup the cache beforehand
• allow the yarn install command to be overwritten