docs: README simplify migration advisory and update links

- Remove stale v5 feature parity warning now that v5 is stable. Replace with concise migration guide reference.
- Fix image embedding to use GitHub-hosted URL
- Update documentation links
- Update supported iOS versions

Author: nan-li

README.md

@@ -7,28 +7,21 @@
 
 ---
 
-#### ⚠️ Migration Advisory for current OneSignal customers
+#### Migrating from v4 or earlier?
 
-Our new [user-centric APIs and v5.x.x SDKs](https://onesignal.com/blog/unify-your-users-across-channels-and-devices/) offer an improved user and data management experience. However, they may not be at 1:1 feature parity with our previous versions yet.
-
-If you are migrating an existing app, we suggest using iOS Phased Rollout capabilities to ensure that there are no unexpected issues or edge cases. Here is the documentation:
-
-- [iOS Phased Rollout](https://developer.apple.com/help/app-store-connect/update-your-app/release-a-version-update-in-phases/)
-
-
-If you run into any challenges or have concerns, please contact our support team at support@onesignal.com
+See our [Migration Guide](MIGRATION_GUIDE.md) for detailed instructions on upgrading to v5.x.x.
 
 ---
 
 [OneSignal](https://www.onesignal.com) is a free email, sms, push notification, and in-app message service for mobile apps. This plugin makes it easy to integrate your native iOS app with OneSignal.
 
-<p align="center"><img src="https://app.onesignal.com/images/ios_10_notification_image.gif" width="400" alt="iOS Notification"></p>
+<p align="center"><img src="https://github.com/user-attachments/assets/8e75f4c6-9ac5-468c-b47b-a111eedb628f" width="400" alt="iOS Notification"></p>
 
 #### Installation
 See OneSignal's [iOS Native SDK Setup Guide](https://documentation.onesignal.com/docs/ios-sdk-setup) for documentation.
 
 #### API
-See OneSignal's [iOS Native SDK API](https://documentation.onesignal.com/docs/ios-native-sdk) page for a list of all available methods.
+See OneSignal's [Mobile SDK reference](https://documentation.onesignal.com/docs/en/mobile-sdk-reference) page for a list of all available methods.
 
 #### Change Log
 See this repository's [release tags](https://github.com/OneSignal/OneSignal-iOS-SDK/releases) for a complete change log of every released version.
@@ -39,4 +32,4 @@ For account issues and support please contact OneSignal support from the [OneSig
 
 #### Supports:
 * Swift and Objective-C Projects
-* Supports iOS 9 to iOS 15
+* Supports iOS 12 to iOS 26