Adds 5.1.2 migration guide to readme (#2781)

diff --git a/packages/go_router/CHANGELOG.md b/packages/go_router/CHANGELOG.md
index b0a6b20..186fabb 100644
--- a/packages/go_router/CHANGELOG.md
+++ b/packages/go_router/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 5.1.5
+
+- Adds migration guide for 5.1.2 to readme.
+
 ## 5.1.4
 
 - Fixes the documentation by removing the `ShellRoute`'s non-existing `path` parameter from it.
@@ -8,9 +12,12 @@
 
 ## 5.1.2
 
-- Exposes uri and path parameters from GoRouter and fixes its notifications.
+- Adds GoRouterState to context.
+- Fixes GoRouter notification.
 - Updates README.
 - Removes dynamic calls in examples.
+- **BREAKING CHANGE**
+  - Remove NavigatorObserver mixin from GoRouter
 
 ## 5.1.1
 
diff --git a/packages/go_router/README.md b/packages/go_router/README.md
index 85f2d91..020039e 100644
--- a/packages/go_router/README.md
+++ b/packages/go_router/README.md
@@ -220,6 +220,7 @@
 - [Migrating to 3.0](https://flutter.dev/go/go-router-v3-breaking-changes)
 - [Migrating to 4.0](https://flutter.dev/go/go-router-v4-breaking-changes)
 - [Migrating to 5.0](https://flutter.dev/go/go-router-v5-breaking-changes)
+- [Migrating to 5.1.2](https://flutter.dev/go/go-router-v5-1-2-breaking-changes)
 
 ## Changelog
 
diff --git a/packages/go_router/pubspec.yaml b/packages/go_router/pubspec.yaml
index 5ffc17e..3973a2a 100644
--- a/packages/go_router/pubspec.yaml
+++ b/packages/go_router/pubspec.yaml
@@ -1,7 +1,7 @@
 name: go_router
 description: A declarative router for Flutter based on Navigation 2 supporting
   deep linking, data-driven routes and more
-version: 5.1.4
+version: 5.1.5
 repository: https://github.com/flutter/packages/tree/main/packages/go_router
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router%22