add package-path input

[llaenowyd]

For #13 .

[manovotny]

@llaenowyd thanks for the contribution! 🎉 I think the change makes sense. I am curious though, what would this look like to consume in a monorepo? What does the GitHub Action setup look like? You have a screenshot or a link to a repo?

[llaenowyd]

I cannot recall precisely. The idea was that a monorepo may have more than one package that it might publish to npm, and that it might publish a package whose package.json is not the root one. I think this would be true about any monorepo from which a package is published to npm.

By allowing the developer to optionally specify the relative path to the pertinent package.json, an action can be written that publishes a single package from a monorepo.

The trigger, as I alluded to in the related issue, would also need to be package specific, as there would not necessarily be a singular release version for the git repository.

[itsjwala]

@llaenowyd - thanks for this PR 🙌

@manovotny - we use lerna to manage monorepo setup in the https://github.com/percy/cli repo.

could you have a look at it 🙇 ? We'd want support like this in monorepo setup.