package property
The package that ships the plugin under test, by its pubspec name, or null to leave the question unasked.
Given, plugin.manifest fails a plugin whose namespace is not it: a
plugin names itself after its package, and one that names itself
after one of the engine's (flutter3d_post.glow from acme_post)
would otherwise be believed to be the engine's own and skip the
namespace and replace rules.
Implementation
final String? package;