Improve appearance of Readme image in github dark mode (#2431)

Author: boomskats

README.md

@@ -70,7 +70,8 @@ For a quick first impression follow the instructions of this
 
 ## Supported setups of Postgres and Applications
 
-![Features](docs/diagrams/neutral_operator.png)
+![Features](docs/diagrams/neutral_operator_dark.png#gh-dark-mode-only)
+![Features](docs/diagrams/neutral_operator_light.png#gh-light-mode-only)
 
 ## Documentation