Clarify offline caching behavior of Flutter SDK (#6069)

Author: cstavitsky

src/platform-includes/getting-started-primer/flutter.mdx

@@ -11,6 +11,8 @@ Features:
   - ObjC, Swift, and C for iOS and macOS
   - Flutter and Android encapsulated exceptions (PlatformException)
 - Offline storage of events
+  - Android: Offline caching when a device is offline; we send a report once the application is restarted
+  - iOS: Offline caching when a device is unable to connect; we send a report once we receive another event
 - Events [enriched](/platforms/flutter/enriching-events/context/) with device data
 - Breadcrumbs automatically captured:
   - by the [Dart SDK](/platforms/dart/enriching-events/breadcrumbs/#automatic-breadcrumbs)

src/platform-includes/getting-started-primer/javascript.cordova.mdx

@@ -11,6 +11,8 @@ Features:
 - Automatic Native crash [error tracking](/product/issues/) using both [iOS](/platforms/apple/guides/ios/) and [Android](/platforms/android/) supports
   - [Release health](/product/releases/health/) to track crash free users and sessions
 - Offline storage of events
+  - Android: Offline caching when a device is offline; we send a report once the application is restarted
+  - iOS: Offline caching when a device is unable to connect; we send a report once we receive another event
 - Events [enriched](/platforms/javascript/guides/cordova/enriching-events/context/) with device data
 - [Breadcrumbs](/platforms/javascript/guides/cordova/enriching-events/breadcrumbs/) created for location changes, outgoing HTTP requests with XHR and Fetch, console logs, and HTML touch events
 - On-device symbolication for JavaScript (in `Debug` mode)

src/platform-includes/getting-started-primer/react-native.mdx

@@ -8,6 +8,8 @@ Features:
 
 - Automatic Native Crash [Error Tracking](/product/issues/) (using both `sentry-cocoa` & `sentry-android`)
 - Offline storage of events
+  - Android: Offline caching when a device is offline; we send a report once the application is restarted
+  - iOS: Offline caching when a device is unable to connect; we send a report once we receive another event
 - Events [enriched](/platforms/react-native/enriching-events/context/) with device data
 - [Autolinking](https://reactnative.dev/blog/2019/07/03/version-60#native-modules-are-now-autolinked)
 - [Breadcrumbs](/platforms/react-native/enriching-events/breadcrumbs/) created for outgoing `http` request with XHR and Fetch; UI and system events; and console logs