Add alt

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/components/views/elements/ImageView.tsx

@@ -489,6 +489,7 @@ export default class ImageView extends React.Component<IProps, IState> {
                     <img
                         src={this.props.src}
                         style={style}
+                        alt={this.props.name}
                         ref={this.image}
                         className="mx_ImageView_image"
                         draggable={true}