Update README: Change heading overview

README.md

@@ -15,7 +15,7 @@ Static geographical data: https://www2.mmm.ucar.edu/wrf/src/wps_files/
 Compile WRF by the help of https://github.com/lenamueller/compile_WRF_on_Taurus   
 Download ERA5 reanalysis data with ```./CDS_download/download.sh```   
 
-## Overview
+## Overview of nested domains
 <img src="processing/domains.png" alt="domains" width="400"/>   
 
 ## Dependencies (complete)