Add more padding to the left/right of the link preview.

lib/controls/timeline/link_preview_control.dart

@@ -13,7 +13,9 @@ class LinkPreviewControl extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     const width = 128.0;
-    return Container(
+    return Padding(
+      padding: const EdgeInsets.only(left: 8.0, right: 8.0),
+      child: Container(
         decoration: BoxDecoration(
             border: Border.all(width: 0.5),
             borderRadius: BorderRadius.circular(2.0)),
@@ -35,6 +37,7 @@ class LinkPreviewControl extends StatelessWidget {
             ],
           ),
         ),
+      ),
     );
   }
 }