Add Result type for captions

lib/models/search/search_result.dart

@@ -22,5 +22,6 @@ enum ResultType {
   year,
   fileType,
   fileExtension,
+  fileCaption,
   event
 }

lib/ui/viewer/search/result/search_result_widget.dart

@@ -125,6 +125,8 @@ class SearchResultWidget extends StatelessWidget {
         return "Type";
       case ResultType.fileExtension:
         return "File Extension";
+      case ResultType.fileCaption:
+        return "Caption";
       default:
         return type.name.toUpperCase();
     }