Update README.md

add comment about darkmode

examples/send/README.md

@@ -6,3 +6,5 @@
 # Notes
 
 After spawning the container, you may have to adjust the bind volume mount permissions again.
+
+If you want to force darkmode, please read [here](https://github.com/timvisee/send/issues/174#issuecomment-1802243265).