Add preview image

Author: Ben

README.md

@@ -1,6 +1,8 @@
 # GitHub Folder Icon for macOS
 Made so that it fits nicely alongside all the others inside your home directory... or wherever.
 
+![preview image](preview.png)
+
 ## Sources
 - Folder icon: [Coloradan on DeviantArt](http://coloradan.deviantart.com/art/Yosemite-Custom-Folder-459481587)
 - GitHub icon: [Dave Gandy on flaticon](https://www.flaticon.com/free-icon/github-logo_25231)