Invisible crypto: Add FAQ entry that explains verification violation

[BillCarsonFr]

A verification violation happens when a user that was previously verified is not anymore, see:

• Invisible crypto: display a warning when a verified user changes identity #2492
• Invisible crypto: Handle Identity Verification violation after we reset our own identity #2691
  ,
  There is a FAQ entry for TOFU violation, we need a similar one for verification violation

[mxandreas]

@BillCarsonFr Which FAQ link are we currently using for the verification-violation banner? I think it should be linked to the dedicated FAQ entry that we're creating as part of this ticket?