prepare styles to have other images (like avatar) in timeline

src/ui/web/css/timeline.css

@@ -45,7 +45,7 @@ limitations under the License.
     replace with css aspect-ratio once supported */
 }
 
-.message-container img {
+.message-container img.picture {
     display: block;
     position: absolute;
     top: 0;

src/ui/web/session/room/timeline/ImageView.js

@@ -22,6 +22,7 @@ export class ImageView extends TemplateView {
         // replace with css aspect-ratio once supported
         const heightRatioPercent = (vm.thumbnailHeight / vm.thumbnailWidth) * 100;
         const image = t.img({
+            className: "picture",
             src: vm.thumbnailUrl,
             width: vm.thumbnailWidth,
             height: vm.thumbnailHeight,