This commit fixes #4. It replaces the occurrences of the old Gitlab
hostname (ending in st.chulg) with the new one (ending in chuliege.be)
and for those occurrences replaces http with https. This occurred only
in the README.org file.

Additionally, this commit also replaces the hostname of the Shiny
server with the chuliege.be one in the README.org file. Given that the
Shiny server is still (only) available over SSH via its st.chulg
hostname, the CI/CD YAML code doesn't need to be changed.