Added chrome_web_image

Added "chrome_web_image"
https://documentation.onesignal.com/reference/create-notification

1.1.2

Enhancements

• Added channel_for_external_ids field for creating a notification.
• Cleanup of unneeded converters
• Added the country field to DelayedOption

Thanks to @MrTarantula

Fixes wrong error verification

Fixes error code verification and ensure response code is OK or created. Else throw an error.

Added async support

Thanks to @alexey-belous and @kevin-david and mostly to @est1908