Add evaluation of maintainer change

[sdruskat]

On the project website under a new menu item, please write up

1.2 Maintainability (@sdruskat & @thomaskrause) - @bbunzeck to create toc entry in SUMMARY.md without a link.
1.2.1 Case study: maintainer change (@bbunzeck)

Later we'll evaluate how the change went and will document it under

1.2.1 Evaluation of maintainer change documentation