Bump version & update changelog

Author: StevenSorial

packages/go_router_builder/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.0.0
+
+- Route classes now required to use a mixin `with _$RouteName`.
+
 ## 2.9.1
 
 - Fixes an deprecated warning for using withNullability

packages/go_router_builder/pubspec.yaml

@@ -2,7 +2,7 @@ name: go_router_builder
 description: >-
   A builder that supports generated strongly-typed route helpers for
   package:go_router
-version: 2.9.1
+version: 3.0.0
 repository: https://github.com/flutter/packages/tree/main/packages/go_router_builder
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router_builder%22