Improve file organization

[theodore-s-beers]

• Add a DOCS folder, both to relocate some existing materials and as a place to build new docs on topics such as our tech stack (see Document our stack more comprehensively #330)
• Add a TESTS folder

To be discussed further…

[XeniaMonika]

What was the TESTS folder for?

[theodore-s-beers]

This process is underway. We now have DOCS and TESTS folders. (The purpose of the latter is to put some separation between the actual schema and the tests that we use to validate JSON files against it.)

[XeniaMonika]

A couple of questions regarding this issue:

• PROTOCOLS - should they go to the DOCS folder? - should we make a folder for it inside the DOCS folder, or better in the root folder?
• CHANGELOG - also to DOCS? It´s in the SCHEMA folder now
• CONTRIBUTIONS - also to DOCS?