Add setup of IDEs to developer documentation

As a developer/contributor I want to know how to setup my IDE in order to have the correct settings and an easy start.

ACs:

• The IDE settings for the following IDEs are part of the repository:
  • vscode
  • (eclipse)
  • intellij
• The developer documentation/how to contribute docs contains some steps how to setup the IDE.

Decision was taken here: DESHN-51: Align on IDE configuration Fertig