feat(ui): Add theme builder functionality (#3458)

Co-authored-by: Kyle MacDonald <kylemac@users.noreply.github.com>
Co-authored-by: Joe Bell <7349341+joe-bell@users.noreply.github.com>

Author: 3 people

.changeset/tough-lamps-itch.md

@@ -0,0 +1,2 @@
+---
+---

packages/ui/README.md

@@ -10,9 +10,12 @@
 
 # @clerk/ui
 
-> [!WARNING]  
+> [!WARNING]
 > This is an experimental package and work-in-progress. Please come back later 👋
 
+- `src/primitives/*` - the building blocks for AIO components void of any Clerk Elements/logic
+- `src/components/*` - the AIO components built using primitives and Clerk Elements
+
 ## License
 
 This project is licensed under the **MIT license**.