Update README.md

Author: mktk1117

README.md

@@ -8,7 +8,10 @@ terrain can be efficiently generated.
 ![screenshot](doc/main_repo.png)
 ![gif](doc/convex_approximation.gif)
 
-Large update is coming soon. Stay tuned.
+## MEM: Multi-Modal Elevation Mapping
+We are preparing for merging the extended map with multi-modal layers such as semantics.  
+If you want to use the feature now, please checkout 'refactor/semantic_layers' branch.  
+Also check this [paper](https://arxiv.org/abs/2309.16818) about the new extention.  
 
 ## Citing