Document WhyDgml

[kant2002]

I notice that WhyDGML tool introduced, maybe I can put some words about it into Documentation\how-to-debug-compiler-dependency-analysis.md

[MichalStrehovsky]

Yup, a line that the tool exists would be good, thanks. You can link to #7962 for sample output and usage. I don't think we need to inline that part.