addSourceFile method
Creates a new $name.dart file in lib/src/
Imports the library file for this terminal.
Implementation
void addSourceFile(String fileName, String contents, {bool export = true}) {
addOrReplaceFile('lib/src/$fileName.dart', """
import 'package:$name/$name.dart';
$contents
""");
addLibraryExport('src/$fileName.dart');
}