Add .iol extension filter to image dialog. Ref https://github.com/GNS3/gns3-gui/issues/3664

Author: grossmj

src/app/components/image-manager/add-image-dialog/add-image-dialog.component.html

@@ -39,7 +39,7 @@ <h5 *ngIf="uploaderImage.queue.length <= 0">Please Select image</h5>
     <div class="col-md-4 txt-align" *ngIf="uploaderImage.queue.length <= 0">
       <input
         type="file"
-        accept=".bin,.image,.qcow2,.vmdk"
+        accept=".bin,.image,.iol,.qcow2,.vmdk"
         multiple
         #file
         class="non-visible"