dart fix: prefer_single_quotes

Author: M-Ahal

example/lib/platform_page.dart.dart

@@ -68,8 +68,8 @@ class PlatformPage extends StatelessWidget {
               title: 'PlatformListTile',
               builder: (_, platform) => PlatformListTile(
                 leading: Icon(context.platformIcons.book),
-                title: PlatformText("title"),
-                subtitle: PlatformText("subtitle"),
+                title: PlatformText('title'),
+                subtitle: PlatformText('subtitle'),
                 trailing: Icon(context.platformIcons.rightChevron),
                 onTap: () => print('${platform.text} PlatformListTile'),
               ),

lib/src/platform_popup_menu.dart

@@ -243,7 +243,7 @@ class PlatformPopupMenu extends StatelessWidget {
                 key: data?.key,
                 isDefaultAction: data?.isDefaultAction ?? false,
                 isDestructiveAction: data?.isDestructiveAction ?? false,
-                child: data?.child ?? Text(option.label ?? ""),
+                child: data?.child ?? Text(option.label ?? ''),
                 onPressed: data?.onPressed ??
                     () {
                       Navigator.pop(context);
@@ -281,7 +281,7 @@ class PlatformPopupMenu extends StatelessWidget {
               final data = option.material?.call(context, platform(context));
               items.add(PopupMenuItem<PopupMenuOption>(
                 value: option,
-                child: data?.child ?? Text(option.label ?? ""),
+                child: data?.child ?? Text(option.label ?? ''),
                 enabled: data?.enabled ?? true,
                 height: data?.height ?? kMinInteractiveDimension,
                 key: data?.key,