Combine sigstore FAQs into one FAQ /check links and help page

[jonvnadelberg]

Description

There are several FAQs under https://docs.sigstore.dev/ They should be combined into one FAQ with headers for different sections and be placed under the help header.

All links in sigstore docs should be checked to see if they currently work and go to a reasonable location.

Help page maintainers should be checked to see if they are still accurate.