Describe first case study including quantified benefits in PoC demonstrator deliverable document

[MartijnCa]

Use outcomes from #57, #2, and #41, which are expected to be finished by 10th or 17th of july.)

Acceptance criteria:

• The first case study has been fully described in the PoC demonstrator deliverable document
• The quantified economic and societal benefits are included in the description
• Ideas for improving the first case study have been shared and/or documented in the idea column of the project board.