Bump version and add changelog

Author: ThexXTURBOXx

flutter_web_auth_2/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 5.0.0-alpha.3
+
+- 💥 Migrate to Swift Package Manager - see [here](https://docs.flutter.dev/packages-and-plugins/swift-package-manager/for-app-developers) for more info (Thanks to [@lishaduck](https://github.com/lishaduck) in [#165](https://github.com/ThexXTURBOXx/flutter_web_auth_2/pull/165))
+
 ## 5.0.0-alpha.2
 
 - 💥 Even newer Android authentication approach (Thanks to [@titanous](https://github.com/titanous) in [#163](https://github.com/ThexXTURBOXx/flutter_web_auth_2/pull/163))

flutter_web_auth_2/pubspec.yaml

@@ -1,6 +1,6 @@
 name: flutter_web_auth_2
 description: Flutter plugin for authenticating a user with a web service.
-version: 5.0.0-alpha.2
+version: 5.0.0-alpha.3
 resolution: workspace
 homepage: https://github.com/ThexXTURBOXx/flutter_web_auth_2
 repository: https://github.com/ThexXTURBOXx/flutter_web_auth_2