add script for github status sync to be included by others

This adds a generic ci script called github-status-sync.yml to sync the status of a ci pipeline back to github.

To use it include the following in the .gitlab-ci.yml (after it is merged):

include:
  - 'https://codebase.helmholtz.cloud/m-team/tools/ci-voodoo/-/raw/master/ci-include/github-status-sync.yml'

variables:
  UPSTREAM_PROJECT: ORG/REPO

where ORG/REPO is replaced with the name of the organization/user and repository on github.

You also need to add an github personal access token with the repo:status scope (read+write) to Codebase. This is done as a env var (Settings->CI/CD->Variables). The name MUST be GH_STATUS_TOKEN.

If you have multiple repos within the same github organization that has a corresponding subgroup on codebase, you might want to create an access token for this organization that gives access to all or multiple repos at the same time and then can set this access token as a variable in the subgroup - this way you don't have to set it in the individual repos.