On the Docker Hub page, configure the link to the github repo hosting the Dockerfile

[nicolas-heigvd]

It feels quite empty on the Docker Hub, e.g. here https://hub.docker.com/r/baremaps/baremaps
compared to, e.g. https://hub.docker.com/r/osgeo/gdal
where one can spot the github page hosting the Dockerfile which has been used to build''n'push the image to the hub:

it's a "nice to have" feature, but an immensely useful one, especially for newcomers imho.

[bchapuis]

#189 should be fixed before this issue.

[bchapuis]

@nicolas-heigvd I updated the dockerhub page. Let me know if something else is missing.