The plugin can be developed with the example project after running an initial flutter build ios --no-codesign.
If you need to create a new native source file, add it in ios/Classes/, go to example/ios and run pod install. Creating the file in Xcode will work, but it will be referenced with a wrong path, breaking autocompletion.
If you have all of the dependencies installed, you can run make docs and copy the api_docs subdirectories in the documentation repository.
Otherwise, you can build a specific platform:
Run make doc. You will need dartdoc for this: flutter pub global activate dartdoc. You might need to update your $PATH.
iOS requires swift-doc to be installed. Run make doc-ios.
Android doesn't require anything than a standard toolchain. You might need to set Android Studio's JVM as your JAVA_HOME. Run make doc-android.