Export help command

[wilcoxmd]

Overview
Hi! I'm trying to bundle an oclif CLI, and would like to be able to use the help plugin. Based on this example, it seems like we need to be able to import the help command and then re-export it in order to accomplish this.

Currently, this doesn't seem possible because the @oclif/plugin-help package only exports an empty object, rather than any command classes.

Describe the solution you'd like
I'd like to update @oclif/plugin-help to export a commands object containing the help command. There is prior art for this in @oclif/plugin-plugins to follow.

Describe alternatives you've considered
I'm not sure there is another alternative if we want to bundle the help command, but if you see another path, please let me know!

Additional context
Figured I'd open an issue before attempting the change in case there is context I need to be aware of. Happy to help, just let me know if you all are open to this!