[IIIF-148] Add canvas index param

Author: atarix83

src/app/item-page/mirador-viewer/mirador-viewer.component.ts

@@ -36,6 +36,11 @@ export class MiradorViewerComponent implements OnInit {
    */
   @Input() canvasId: string;
 
+  /**
+   * Is used as canvas index of the element to show.
+   */
+  @Input() canvasIndex: string;
+
   /**
    * Hides embedded viewer in dev mode.
    */
@@ -98,6 +103,9 @@ export class MiradorViewerComponent implements OnInit {
     if (this.canvasId) {
       viewerPath += `&canvasId=${this.canvasId}`;
     }
+    if (this.canvasIndex) {
+      viewerPath += `&canvasIndex=${this.canvasIndex}`;
+    }
 
     // TODO: Should the query term be trusted here?
     return this.sanitizer.bypassSecurityTrustResourceUrl(viewerPath);