Add extension https://github.com/riknoll/arcade-state-transitions

Fixes #161

Author: UnsignedArduino

content/extensions/072-riknoll---arcade-state-transitions.md

@@ -0,0 +1,8 @@
+---
+repo: "https://github.com/riknoll/arcade-state-transitions"
+links:
+  - title: Forum post
+    url: "https://forum.makecode.com/t/sprites-not-showing/27957/4?u=unsignedarduino"
+---
+
+This extension makes managing complex state in your MakeCode Arcade games easy! You can set global state or per-sprite level state, register handlers, and more, allowing you to implement complex interactions and abilities much more easily! This adds a `State` category to the toolbox.