lightbox: Make image zoom 10x instead of the default (2.5x)

Fixes: #1091

Author: sm-sayedi

lib/widgets/lightbox.dart

@@ -348,6 +348,7 @@ class _ImageLightboxPageState extends State<_ImageLightboxPage> {
       buildBottomAppBar: _buildBottomAppBar,
       child: SizedBox.expand(
         child: InteractiveViewer(
+          maxScale: 10, // TODO adjust based on device and image size; see #1091
           child: SafeArea(
             child: LightboxHero(
               messageImageContext: widget.messageImageContext,

test/widgets/lightbox_test.dart

@@ -366,6 +366,16 @@ void main() {
       debugNetworkImageHttpClientProvider = null;
     });
 
+    testWidgets('image can zoom up to 10x', (tester) async {
+      prepareBoringImageHttpClient();
+      await setupPage(tester, thumbnailUrl: null);
+
+      check(tester.widget<InteractiveViewer>(find.byType(InteractiveViewer)).maxScale)
+        .equals(10);
+
+      debugNetworkImageHttpClientProvider = null;
+    });
+
     void checkAppBarNameAndDate(WidgetTester tester, String expectedName, String expectedDate) {
       final labelTextWidget = tester.widget<RichText>(
         find.descendant(of: find.byType(AppBar).last,