For example, say you write a foobar_windows
implementation for the (imaginary) foobar plugin.
In an endorsed plugin, the original foobar author
adds your Windows implementation as a dependency
in the pubspec for the app-facing package.
Then, when a developer includes the foobar plugin
in their Flutter app, the Windows implementation,
as well as the other endorsed implementations,
are automatically available to the app.

Non-endorsed federated plugin

If you can’t, for whatever reason, get your implementation
added by the original plugin author, then your plugin
is not endorsed. A developer can still use your
implementation, but must manually add the plugin
to the app’s pubspec file. So, the developer
must include both the foobar dependency and
the foobar_windows dependency in order to achieve
full functionality.