docs(firebase_analytics): example app initialization and docs support status

[pr-Mais]

Description

Fixed the initialization part in the example app for firebase_analytics and addd the support status section to show which plugins/platforms currently doesn't support the Dart-only initialization.

Related Issues

closes #7639
closes #7543

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[github-actions]

Visit the preview URL for this PR (updated for commit a34cc44):

https://flutter-firebase-docs--pr7745-analytics-example-uc6ihq0q.web.app

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[russellwheatley]

A few small changes from me. I think you'll also need to add back in the google service file for example/android as well.

[pr-Mais]

Yeah it's there https://github.com/FirebaseExtended/flutterfire/tree/analytics-example/packages/firebase_analytics/firebase_analytics/example/android/app

[Ehesp]

Is the PR title correct here? It says fix but only applies docs and examples changes so shouldn't change versions of anything?

[pr-Mais]

yes I agree, docs could be?