Remove docsify from core repository

[juliapampus]

Feature Request

Remove docsify-specific files from /docs. The general documentation framework will be placed in a separate repository.

Which Areas Would Be Affected?

docs

Why Is the Feature Desired?

Clean up /docs, restructure GitHub pages

Solution Proposal

• Remove files (_helper, _media, README.md, package.json, index.html, _sidebar.md, _navbar.md, _coerpage.md, .nojekyll, user, adopter, developer/README.md, overview)
• Prototypic Sequence for Contract Offer Creation broken
• Add toc to https://github.com/eclipse-dataspaceconnector/DataSpaceConnector/blob/main/docs/README.md
• Add toc to extensions and launchers
• Add docs section to readme of other repos (like in MVD)

Type of Issue

cleanup

Checklist

• assigned appropriate label?
• Do NOT select a milestone or an assignee!