Instruct about the possibility of creating a persistent storage when there is none
From https://gitlab.tails.boum.org/tails/blueprints/-/wikis/Persistent-Storage-redesign:


Such a message would help solving 2 issues from the user testing of the Additional Software beta:
- P3 expected the persistent storage to appear in Tails Greeter (before she started the session and created one).
- 3 participants out of 5 missed the new field “Encrypted Persistent Storage” the first time it appeared. See also #15573.
I'm not sure the image will look good on the actual screen.