change to backer link

Author: alexweissman

README.md

@@ -6,8 +6,8 @@
 [![Join the chat at https://chat.userfrosting.com/channel/support](https://demo.rocket.chat/images/join-chat.svg)](https://chat.userfrosting.com/channel/support)
 [![Backers on Open Collective](https://opencollective.com/userfrosting/backers/badge.svg)](#backers) [![Sponsors on Open Collective](https://opencollective.com/userfrosting/sponsors/badge.svg)](#sponsors)
 
-<a href="https://opencollective.com/userfrosting/donate" target="_blank">
-  <img src="https://opencollective.com/userfrosting/donate/button@2x.png?color=blue" width=300 />
+<a href="https://opencollective.com/userfrosting#backer" target="_blank">
+  <img src="https://opencollective.com/userfrosting/donate/button.png?color=blue" width=300 />
 </a>
 
 If you simply want to show that you like this project, or want to remember it for later, you should **star**, not **fork**, this repository.  Forking is only for when you are ready to create your own copy of the code to work on.