Update README.md
Minor update to readme
<h2>How to use the sample</h2>
-<p>Tap anywhere on the map. An orange marker will show the tapped location. A blue marker will show the polygon's nearest vertex to the tapped location. A red marker will show the nearest coordinate on the geometry.</p>
+<p>Tap anywhere on the map. An orange marker will show at that tapped location. A blue marker will show the polygon's nearest vertex to the tapped location. A red marker will show the nearest coordinate within the polygon geometry.</p>
<h2>How it works</h2>
