Clean up design

lib/views/image_viewer.dart

@@ -2,7 +2,6 @@ import 'package:cached_network_image/cached_network_image.dart';
 import 'package:famedlysdk/famedlysdk.dart';
 import 'package:fluffychat/components/matrix.dart';
 import 'package:fluffychat/utils/app_route.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:photo_view/photo_view.dart';
 import 'package:url_launcher/url_launcher.dart';
@@ -13,15 +12,11 @@ class ImageViewer extends StatelessWidget {
   const ImageViewer(this.mxContent);
 
   static show(BuildContext context, MxContent content) {
-    if (kIsWeb) {
-      launch(content.getDownloadLink(Matrix.of(context).client));
-    } else {
-      Navigator.of(context).push(
-        AppRoute(
-          ImageViewer(content),
-        ),
-      );
-    }
+    Navigator.of(context).push(
+      AppRoute(
+        ImageViewer(content),
+      ),
+    );
   }
 
   @override
@@ -29,6 +24,9 @@ class ImageViewer extends StatelessWidget {
     final String url = mxContent.getDownloadLink(Matrix.of(context).client);
     return Scaffold(
       appBar: AppBar(
+        brightness: Brightness.dark,
+        backgroundColor: Colors.black,
+        iconTheme: IconThemeData(color: Colors.white),
         actions: <Widget>[
           IconButton(
             icon: Icon(Icons.file_download),