Update README.md

Author: kristoferbaxter

README.md

@@ -4,7 +4,7 @@
 
 Uses native compression from Node Core, attempts to parallelize compression work across available CPUs, and requires Node >= `10.16`.
 
-![alt-text](https://github.com/ampproject/filesize/raw/master/src/preview.gif)
+![Interactive UI Processing Large Files](https://github.com/ampproject/filesize/raw/master/preview.gif)
 
 ## Installation