docs(firebase_analytics): add more documentation for logEvent

[nilsreichardt]

Description

When I used logEvent I tried to get Dart documentation about the limitations of logEvent. However, there was no helpful information (like length of name, reversed names, data types for parameters). Therefore, I copied the documentation from firebase.google.com/docs into the Dart source code.

Copied from: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics#public-void-logevent-string-name,-bundle-params

Related Issues

...

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• I signed the CLA.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change.
• No, this is not a breaking change.