Fix media description in various media modals (#8678)

app/javascript/mastodon/features/ui/components/media_modal.js

@@ -149,7 +149,7 @@ export default class MediaModal extends ImmutablePureComponent {
             startTime={time || 0}
             onCloseVideo={onClose}
             detailed
-            description={image.get('description')}
+            alt={image.get('description')}
             key={image.get('url')}
           />
         );

app/javascript/mastodon/features/ui/components/video_modal.js

@@ -24,7 +24,7 @@ export default class VideoModal extends ImmutablePureComponent {
             startTime={time}
             onCloseVideo={onClose}
             detailed
-            description={media.get('description')}
+            alt={media.get('description')}
           />
         </div>
       </div>

app/javascript/mastodon/features/ui/components/zoomable_image.js

@@ -137,6 +137,7 @@ export default class ZoomableImage extends React.PureComponent {
           role='presentation'
           ref={this.setImageRef}
           alt={alt}
+          title={alt}
           src={src}
           style={{
             transform: `scale(${scale})`,

app/javascript/mastodon/features/video/index.js

@@ -252,11 +252,12 @@ export default class Video extends React.PureComponent {
   }
 
   handleOpenVideo = () => {
-    const { src, preview, width, height } = this.props;
+    const { src, preview, width, height, alt } = this.props;
     const media = fromJS({
       type: 'video',
       url: src,
       preview_url: preview,
+      description: alt,
       width,
       height,
     });