use map.png for compbined leaflet map pics display in docs (#42)

Author: RandomFractals

README.md

@@ -8,7 +8,7 @@
 
 <h1 align="center">
   <img width="600" height="159" src="docs/images/leaflet-logo.png" />
-  <img width="128" height="128" src="resources/icons/leaflet-map.png" />
+  <img width="128" height="128" src="resources/icons/map.png" />
   <br />
   Leaflet Map 🗺️ for Notebook 📓 cell ⌗ data outputs
 </h1>