iOS change app icon with fastlane

ios-change-appicon.rb

    unless iconDownloadUrl.empty?
      tempfile = Down.download(iconDownloadUrl)
      appicon(
        appicon_image_file: tempfile.path,
        appicon_devices: [:iphone, :ios_marketing],
        appicon_path: Dir.pwd + "#{placeHolderPath}/Placeholder.xcassets",
        remove_alpha: true,
      )
    end