Don't show bookmark button by default

[MichaelDeBoey]

Closes #4
Closes #5

BREAKING CHANGE: Bookmark button isn't enabled by default anymore

[robinmetral]

Great! Just for the sake of doing things right, let's add a small deprecation notice that is logged if users attempt to pass any of the legacy plugin options 🙂

It's fairly straightforward: we need to create a gatsby-node.js file and add something like this:

const deprecationWarning = `From now on, you can use the gatsby-plugin-pinterest 'saveButton' option to show the Pinterest Save button on images.
See https://github.com/robinmetral/gatsby-plugin-pinterest#usage`;

exports.onPreInit = ({ reporter }, options) => {
  if (options.tall || options.round) {
    reporter.warn(deprecationWarning);
  }
};

Inspired by gatsby-plugin-google-analytics

(edit: I found that the message must be broken into several lines, the console cannot handle line breaks)

[robinmetral]

🎉 This PR is included in version 2.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀