async generateDefaults () {
    const pkg = (await common.readMetadata(this.userSupplied)) || {}

    const authors = pkg.author ? [typeof pkg.author === 'string' ? parseAuthor(pkg.author).name : pkg.author.name] : undefined

    this.defaults = Object.assign(common.getDefaultsFromPackageJSON(pkg), {
      version: pkg.version || '0.0.0',

      copyright: pkg.copyright || (authors && `Copyright \u00A9 ${new Date().getFullYear()} ${authors.join(', ')}`),
      authors: authors,
      owners: authors,

      exe: pkg.name ? `${pkg.name}.exe` : 'electron.exe',
      icon: path.resolve(__dirname, '../resources/icon.ico'),
      animation: path.resolve(__dirname, '../resources/animation.gif'),

      iconNuget: undefined,

      tags: [],

      certificateFile: undefined,
      certificatePassword: undefined,
      signWithParams: undefined,

      remoteReleases: undefined,

      noMsi: false
    })

    return this.defaults
  }
Get the hash of default options for the installer. Some come from the info
read from `package.json`, and some are hardcoded.