show light/dark logo of Ditto in Readme depending on GH theme

README.md

@@ -1,7 +1,9 @@
 <a href="https://eclipse.org/ditto/">
-  <img src="https://eclipse.org/ditto/images/ditto.svg" alt="Ditto Logo" width="100%" height="250">
+  <img src="https://raw.githubusercontent.com/eclipse/ditto/master/logo/ditto_fordarkbg.svg?sanitize=true#gh-dark-mode-only" alt="Ditto Logo dark" width="100%" height="250">
+  <img src="https://raw.githubusercontent.com/eclipse/ditto/master/logo/ditto.svg?sanitize=true#gh-light-mode-only" alt="Ditto Logo light" width="100%" height="250">
 </a>
 
+
 # Eclipse Ditto™
 
 [![Join the chat at https://gitter.im/eclipse/ditto](https://badges.gitter.im/eclipse/ditto.svg)](https://gitter.im/eclipse/ditto?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)