[Compendium] Guide the user when searching for specific information about the OEF

What is this issue about?

As we discussed at the project meeting in Kassel:

The compendium will exist alongside the Academy and the Open Energy Platform website. We do not want to confuse users by presenting the compendium as another source of information. Therefore, clear guidance needs to be given on which resource is aimed at which goal (what information the user can get).

This affects all the resources mentioned (oep/academy/open energy platform/...maybe more) and requires a restructuring of the visible content.

What needs to be done:

• add the compendium to the open energy platform homepage.
• find out how to create a link between oep - compendium - academy
• create a smart and comprehensive homepage for the compendium (show the user which resource offers which information)
• include paths for different users (personas), as not all users want to have all the information, but rather want to get certain information as quickly as possible