[CI]: serve demo pages

We need artifacts to deploy the demo (or different versions of the demo).

We could add a gitlab.ci.yml file, with a job that runs compile.sh and produces a job artefact, which is a job that will produce a list of files that can be downloaded, or in our case served so that we can test multiple setups.

to setup a runner to test locally :

Settings - CI/CD - Runners - Set up a specific runner manually

an example of a zip file that contains build artifacts can be found in https://code.videolan.org/jbk/vlc.js/-/tree/deploy-test