MediaAttachmentGrid: improve layout as length % 2

src/timelines/MediaAttachmentGrid.tsx

@@ -51,9 +51,19 @@ const MediaAttachmentGrid: Component<{
     setViewerIndex(index);
   };
 
+  const columnCount = () => {
+    if (props.attachments.length === 1) {
+      return 1;
+    } else if (props.attachments.length % 2 === 0) {
+      return 2;
+    } else {
+      return 3;
+    }
+  };
+
   css`
     .attachments {
-      column-count: ${(props.attachments.length === 1 ? 1 : 3).toString()};
+      column-count: ${columnCount.toString()};
     }
   `;
   return (