Adds instructions how to add a Software Spotlight
To support external developers in adding their Software Spotlights to hifis.net, I added a section to CONTRIBUTING.md where the workflow and minimum requirements are described. I added a table of contents to the file too, and since I was using a markdown formatter, all tables in the document were formatted to a readable format.
@konrad @jandt-desy @frust45 Do you have any suggestions? Should the instructions go elsewhere? If everything is fine I'd be happy about your approval
Edited by Christian Meeßen