Added support for content templates (i.e. whatsapp)

[alexw23]

Added support for sending content templates. This also adds support for whatsapp (inherity).

Added documentation about this.

See here for more details: https://www.twilio.com/docs/content/send-templates-created-with-the-content-template-builder#how-to-add-senders-to-a-your-sender-pool

[evaldorcardoso]

Hello @onlime , is there any chance of this being implemented in the project? I am implementing this package in my project and I need to use content templates and would like to use this solution. Thanks a lot!

[alexw23]

@evaldorcardoso just use my fork for now if you need.

"require": [
        ...
        "laravel-notification-channels/twilio": "dev-add-content-messages-v3"
],
"repositories": [
        ...
        {
            "type": "vcs",
            "url": "https://github.com/alexw23/twilio"
        }
],