Information on how to build INSPIRE validator and where source code can be found

[stempler]

This repository contains binary releases of the INSPIRE validator but I can't find any information on where the used sources are located or how to build the application. It would be great if the maintainers could be transparent on which source code is used and how the INSPIRE validator is built.

It would be very helpful when looking into problems with the validator to be able to identify the source code that is used in a specific release. It would also be helpful sometimes to be able to debug certain issues.
Additionally this would open up the INSPIRE validator to external contributions.

Right now the INSPIRE validator seems like a black box with only a vague idea on what components are used inside (etf-webapp, test drivers, etc.) and limited possiblities to adapt running it (e.g. modify Dockerfile, entrypoint script etc.).