Autogenerate the list of users from USERS.md in each subproject repos

[terrytangyuan]

We had a script to fetch all USERS.md from all subproject repos and then render the logos dynamically on our website. However, for our new version of website, new users need to be added manually and I don't think this gets updated much. https://github.com/argoproj/argo-site/tree/master/content/members

From @alexmt:

we did not update script after migrating to new website. In old web site we were using logos hosted by clearbit.com so it was enough to just generate list of links. We new design we need to download image.

Just in case here is old script. https://github.com/argoproj/argo-site/blob/faf830d9e19260f69ade594a2857499fa8c31c6c/scripts/logos.sh We definitely can modify it to work with the new website