Refresh landing page contents

[viccuad]

A lot of cool features have been added, we should refresh the landing page contents.

Acceptance criteria

• Use "The Universal Policy Engine" tagline
• Prioritize Policy Consumer persona, as stated in Feat: Reorg docs following Diataxis doc system docs#152
• New diagram for the "how it works" with newer components
• List newer features: Audit Scanner, Raw policies, Policy SDKs, PSP migration, Sigstore, monitor mode, ArtifactHub..
• Expand "What is Kubewarden", with the rest of missing personas (in addition to "As a Policy author", "As a Kubernetes Operator" that are there)