Add DigitalOcean referral badge

Added a DigitalOcean referral badge to the README.

Author: sethhorsley

README.md

@@ -26,3 +26,5 @@ gem "ruby_ui", path: "../ruby_ui"
 This workflow allows you to iterate quickly on components while maintaining the gem's structure.
 
 Would you like me to expand on any part of the contributing guide?
+
+[![DigitalOcean Referral Badge](https://web-platforms.sfo2.cdn.digitaloceanspaces.com/WWW/Badge%201.svg)](https://www.digitalocean.com/?refcode=0fdaefc76c39&utm_campaign=Referral_Invite&utm_medium=Referral_Program&utm_source=badge)