update code snippets

Author: buenaflor

platform-includes/configuration/auto-session-tracking/flutter.mdx

@@ -4,9 +4,8 @@ To benefit from the health data, you must use at least version 4.0.0 of the Flut
 
 By default, the session is terminated once the application is in the background for more than `30 seconds`. You can change this default by setting the `autoSessionTrackingInterval` option to a `Duration` of your choosing.
 
-```dart
+```dart {2}
 SentryFlutter.init((options) {
-  // Change timeout duration until session is terminated in background
   options.autoSessionTrackingInterval = const Duration(seconds: 60)
 });
 ```
@@ -15,9 +14,8 @@ SentryFlutter.init((options) {
 
 If you'd like to opt out of capturing sessions, set the `enableAutoSessionTracking` option to `false`. If you disable this feature, release health will not be available.
 
-```dart
+```dart {2}
 SentryFlutter.init((options) {
-  // Disable auto session tracking
   options.enableAutoSessionTracking = false;
 });
 ```

platform-includes/enriching-events/attach-screenshots/flutter.mdx

@@ -1,13 +1,11 @@
 Enable screenshots by setting the `attachScreenshot` option to `true` and wrap your root widget with `SentryWidget`.
 
-```dart
+```dart {3, 6-8}
 await SentryFlutter.init(
   (options) {
-    // Set the option to true to enable capturing screenshots
     options.attachScreenshot = true;
   },
   appRunner: () => runApp(
-    // Wrap your root widget with the [SentryWidget] widget.
     SentryWidget(
       child: MyApp(),
     ),
@@ -21,14 +19,22 @@ You can filter your screenshots by using the `beforeScreenshot` callback, which
 
 If the callback returns `false`, the screenshot will not be attached.
 
-```dart
-await SentryFlutter.init((options) {
-  options.beforeScreenshot = (event, {hint}) {
-    // Example: based on some condition you can decide to attach the screenshot or drop it
+```dart {4-10}
+await SentryFlutter.init(
+  (options) {
+    options.attachScreenshot = true;
+    options.beforeScreenshot = (event, {hint}) {
+    // Based on some condition you can decide to attach the screenshot or drop it
     if (event.throwable is MyImportantException) {
       return true;
     }
-    return false;
-  };
-});
+      return false;
+    };
+  },
+  appRunner: () => runApp(
+    SentryWidget(
+      child: MyApp(),
+    ),
+  ),
+);
 ```