[Documentation] add to FAQ: what score is needed to earn Certification?

[lixuna]

[Documentation] add to FAQ: What tests are included in the CNF Certification?

Short description:

• add a Q&A to the FAQ explaining that 10 or more essential tests must pass to earn certification
• link to /docs/CNFCertification-1.1-beta.md

Child of:

20

[agentpoyo]

https://github.com/cncf/cnf-certification/pull/59