Improve popup positioning based on rect's postion and not on click's X,Y coordiantes.

Closes #3

service.js

@@ -1145,8 +1145,14 @@ class BesService {
     hits.forEach(({ el, match }) => {
       popup.setContent(el, match, this, this.isContentEditable())
       this.highlightMistake(match)
+      const containerRect = this.hostElement.getBoundingClientRect()
+      match.highlights.forEach(rect => {
+        const clientX = rect.x + containerRect.left
+        const clientY =
+          rect.y + containerRect.top + rect.height - this.hostElement.scrollTop
+        popup.show(clientX, clientY, this)
+      })
     })
-    popup.show(source.clientX, source.clientY, this)
   }
 
   /**