src/common/load-plugins.js/getPluginsFromPackage
function getPluginsFromPackage(pkg) {
  if (!pkg) {
    return [];
  }
  const deps = Object.assign({}, pkg.dependencies, pkg.devDependencies);
  return Object.keys(deps).filter(
    dep =>
      dep.startsWith("prettier-plugin-") || dep.startsWith("@prettier/plugin-")
  );
}