flutter/flutter#32329 introduces some configurable changes to the flutter behavior, which need to be documented in this page:

• https://docs.flutter.dev/development/platform-integration/web/initialization

The following needs to be documented:

• New engineInitializer.initializeEngine(configuration) API.
  • Attributes that can be passed as keys for the configuration object.
  • Deprecation of the window global variables that used to allow this before.
• Documentation about the hostElement behavior (null element vs non-null).
• ??? more?

See the design doc for some literature, and the related issues/PRs for more info.