Alignment SD-JWT-VC and SD-JWT

[m-basili]

This PR aims to align technical specifications with SD-JWT-VC (Draft 04) and SD-JWT (Draft 10).

Content:

• Added vctm optional parameter in the PID/(Q)EAA SD-JWT header
• Added x5c optional parameter in the PID/(Q)EAA SD-JWT header
• Updated vct values parameter in the PID/(Q)EAA SD-JWT payload
• Added information related to user authentication in the PID/(Q)EAA SD-JWT payload
• Description of Credential Metadata JSON Document's retrieve method
• Added Digital Credential Metadata Type parameters and relative example
• Removed theme customization for docs italia (closes #377)
• Example codes updated and moved in JSON files
• Link references updated
• closes #210