For more information on federated plugins,
why they are useful, and how they are
implemented, see the Medium article by Harry Terkelsen,
How To Write a Flutter Web Plugin, Part 2.

Specifying a plugin’s supported platforms

Plugins can specify the platforms they support by
adding keys to the platforms map in the
pubspec.yaml file. For example,
the following pubspec file shows the
flutter: map for the hello plugin,
which supports only iOS and Android:

flutter

plugin

platforms

android

package

com.example.hello

pluginClass

HelloPlugin

ios

pluginClass

HelloPlugin

environment

sdk

>=2.1.0

<3.0.0"