CLI and Controller Installation Instructions

[fabianburth]

Description
As preparation for the release, our ./README.md needs a short installation section for installing the new controllers on your cluster.
That installation section should essentially just point to our helm chart and how to apply this to the cluster.

Mention that you need flux and kro for productive setups.

Also check the README.md as it might be deprecated at some points and fix them.

Done Criteria

• Code has been reviewed by other team members
• Analysis of existing tests (Unit and Integration)
• Unit Tests created for new code or existing Unit Tests updated
• Integration Test Suite updated (includes deletion of existing unnecessary Integration Test and/or creation of new ones if required)
• Enduser Documentation updated (if applicable)
• Internal technical Documentation created/updated (if applicable)
• Successful demonstration in Review