Migrate guide/overview

Signed-off-by: Gavin Zhao <git@gzgz.dev>

Author: GZGavinZhao

_config.yml

@@ -21,7 +21,7 @@ port: 5000
 www: https://dart.dev
 webdev: https://dart.dev/web
 dartlang: https://dart.dev
-angulardart: https://angulardart.dev
+angulardart: https://angulardart.xyz
 angular: https://angular.io
 dart_vm:  https://dart.dev/server
 flutter:  https://flutter.dev

src/guide/index.md

@@ -86,4 +86,4 @@ Please tell us about any issues you find:
   [site-angulardart issue
   tracker]({{site.repo.this}}/issues).
 * To report issues with **AngularDart** itself, use the
-  [Angular issue tracker](https://github.com/dart-lang/angular/issues).
+  [Angular issue tracker](https://github.com/angulardart-community/angular/issues).