Could not get unknown property 'android' for project ':flutter_webview_plugin' of type org.gradle.api.Project.

I'm trying to use the Flutter Webview Plugin but I keep getting the error described in the title and I don't know why. I added `flutter_webview_plugin: ^0.3.5` to my `dependencies` in the `pubspec.yaml` and did `$ flutter pub get`. Do I need to add anything else or maybe something to the `build.gradle` like `implementation...` or something like that? Can you help me please?