Added Prior indicator to viewport overlay based on oldest study date

Packages/viewerbase/components/viewer/viewportOverlay/viewportOverlay.html

@@ -3,7 +3,7 @@
         <div class="topleft dicomTag">
             <div>{{formatPN patientName}}</div>
             <div>{{patientId}}</div>
-            <div></div>
+            <div class='priorIndicator'>{{prior}}</div>
         </div>
         <div class="topright dicomTag">
             <div>{{studyDescription}}</div>