Otherwise, manual build

Now, builds are optimized using a custom Docker image. High ressources 
usage during build should no longer be an issue

modification des liens du sommaire + maj de la semaine des médians en semaine de régulation

See merge request elus_etu/elus_etu.gitlab.utc.fr!1

Commit original: 
elus_etu/website@ac199691

When using 'podman push', for some reason the image manifest isn't 
accessible in the Docker Hub. This commit uses an image pushed by 
'docker':

docker pull am97/jekyll-indigo-build:latest
docker tag am97/jekyll-indigo-build:latest 
am97/jekyll-indigo-build:docker-20200401
docker push am97/jekyll-indigo-build:docker-20200401

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