Use Pages when publishing repo to GitLab or GitHub

@pserwylo wrote:

think pointing people to fetch raw files from gitlab.com is going to be a tad unethical. They wont have a CDN in front of the raw git files, and it will thus take more processing on their end each time someone requests a file. However if we are able to get them onto gitlab.io pages then it would aleviate most of those concerns.

So let's add a .gitlab-ci.yaml and the equvalent for github before pushing the repo.

We should also not to forget to also adjust get_raw_mirror(url) to the new URL (and maybe also rename the method).