Have illustrations to support our explanation of Tails

See the tent metaphor on https://tails.boum.org/blueprint/explain_tails/.

I think I should first work on #16536 until I have a good structure and then work on integrating visuals into it.

See also the design brief that we wrote with Simply Secure:

https://docs.google.com/document/d/1dSEs1p7_fkxJiDZnF-yf5AVrymbhowobIS_cUVIqOKE/edit#

Blueprint: https://tails.boum.org/blueprint/explain_tails/

Parent Task: #9814

Related issues

• Blocked by #16536
• Blocks #16688
• Blocked by #15886 (closed)

Original created by @sajolida on 16538 (Redmine)