Update README.md

Author: mktk1117

README.md

@@ -10,7 +10,7 @@ terrain can be efficiently generated.
 
 ## 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.  
+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.  
 ![screenshot](doc/overview.png)