Update the changelog and pubspec

Author: StevenSorial

packages/go_router_builder/CHANGELOG.md

@@ -1,6 +1,7 @@
-## NEXT
+## 3.1.0
 
 - Restricts `build` to versions less than 2.5.0.
+- Make the mixin public if the route class is not in the same file.
 
 ## 3.0.1
 

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: 3.0.1
+version: 3.1.0
 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