Move attestation use cases mentioned in † and in the end of ‡ to its own page as it has high re-use value

[SmartLayer]

† https://github.com/TokenScript/documents/blob/main/src/concept/Attestation.md
‡ https://github.com/TokenScript/documents/blob/main/src/faq/attestation_vs_verifiable_credentials.md