!! I don't have server (but my website is on GitLab's server)
It is possible to redirect my www.maudbausier.com domain to my GitLab Page maudb.gitlab.io/dok but this means that maudbausier.com doesn't exist by itself. It could be more interesting to "double" the content on both domain names to have aliases for each of them (ex: maudbausier.com/about).
DNS (Domain Name System)
In this case, it is thus more interesting to modify the DNS zone because the DNS zone allows to make the link between your domain name (here www.maudbausier.com) and the servers that manage your services (here gitlab).
How to: on GitLab
gitlab.com > Sign In > Maud Bausier > dok > settings > pages > New Domain