Create blueprint on user survey (#14545)

wiki/src/blueprint/user_survey.mdwn

+[[!tails_ticket 14545]]
+
+Related blueprints:
+
+- [[blueprint/better_metrics]]
+- [[blueprint/interviews]]
+- [[blueprint/personas]]
+
+Similar surveys
+---------------
+
+- Matomo
+  - <https://matomo.org/blog/2011/06/piwik-community-survey-here-are-the-results/>
+  - <https://survey.piwik.org/index.php/151125>
+  - <https://matomo.org/blog/2017/11/community-survey-revealed-discover-the-profile-of-a-piwik-user/>
+
+Possible research questions
+---------------------------
+
+- Size of user base
+
+  - How many users do we really have?
+  - Right now we only have number of boots per day but combining this
+    with how frequently people use Tails, we could extrapolate rough
+    number of users and maybe usage categories (fraction of frequent
+    users and occasional users, etc.).
+
+- Technical skills
+
+  - How technically skilled are our users?
+  - How big is the difference between the technical skills of our target
+    audience and real audience?
+  - Is there a match between how hard Tails is to use and the skills of
+    our actual users?
+
+- Region
+
+  - Is Tails useful and accessible by a global audience?
+  - Information on where Tails is used the most is very helpful for
+    fundraising, outreach, or translation efforts.
+
+- User tasks
+
+  - What are people using Tails the most?
+  - This would help us clarify what are the most important features of
+    Tails and prioritize incremental improvements.
+  - What is missing the most in Tails?
+  - This would help us build a better roadmap.