UI documentation (#11262)

* Rough in UI docs

* Fix links

* Table documentation

* Forms

* search

* Notifications

docs/mkdocs.yml

@@ -91,6 +91,7 @@ nav:
       - Privacy: privacy.md
   - Concepts:
     - Terminology: concepts/terminology.md
+    - User Interface: concepts/user_interface.md
     - Threat Model: concepts/threat_model.md
     - Physical Units: concepts/units.md
     - Companies: concepts/company.md