Create high-level overview of type relations

[acka47]

...with gliphy in confluence. Starting with straightforward relations leaving things to be discussed for a later point.

[acka47]

First draft at https://dienst-wiki.hbz-nrw.de/x/fYDqPw

[acka47]

In the next version we should address the following requirement from #432 (comment):

What relations do we need between the different types of resources? Lots of them are straightforward but especially the relations between different projects and products wil need some thought. (In the diagram I used uses, improves & updates but we probably should start with only two broader defined relations. Or we might even makes these relations separate nodes to add more context/descriptions to them.)