Adds semantic labels to images and modal close button (#56)

* Added semantic labels to images.

* Reverting project file.

* Semantic label for close button.

veggieseasons/lib/screens/details.dart

@@ -76,6 +76,7 @@ class DetailsScreen extends StatelessWidget {
             child: Image.asset(
               veggie.imageAssetPath,
               fit: BoxFit.cover,
+              semanticLabel: 'A background image of ${veggie.name}',
             ),
           ),
           Positioned(