The try out URL has changed

I discovered this nice tool through Adafruit : https://learn.adafruit.com/next-level-makecode-arcade-games/asset-tool#asset-conversion-3-8
The URL here was not working anymore, but the URL from the article still works.

README.md

@@ -4,7 +4,7 @@ A simple tool for converting images into pxt-arcade's format.
 
 ## Try it out
 
-https://riknoll.github.io/pxt-editor-extension-sample
+https://riknoll.github.io/pxt-arcade-asset-tool/
 
 ## Build