Update image viewer to have description

lib/screens/image_viewer_screen.dart

@@ -11,18 +11,30 @@ class ImageViewerScreen extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(),
-      body: Stack(
-        children: [
-          Container(
-              color: Theme.of(context).backgroundColor,
-              height: MediaQuery.of(context).size.height,
+        appBar: AppBar(),
+        body: Column(
+          mainAxisAlignment: MainAxisAlignment.start,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Expanded(
               child: InteractiveViewer(
-                child: CachedNetworkImage(imageUrl: attachment.uri.toString()),
+                clipBehavior: Clip.none,
+                constrained: true,
                 maxScale: 10.0,
-              )),
-        ],
-      ),
-    );
+                scaleFactor: 0.1,
+                child: CachedNetworkImage(imageUrl: attachment.uri.toString()),
+              ),
+            ),
+            if (attachment.description.isNotEmpty)
+              Padding(
+                padding: const EdgeInsets.only(
+                  left: 8.0,
+                  right: 8.0,
+                  bottom: 8.0,
+                ),
+                child: Text(attachment.description),
+              ),
+          ],
+        ));
   }
 }