feat: added whatsapp-with-vonage function template in C++

[FreSauce]

What does this PR do?

Adds a function template for Whatsapp with Vonage in C++.

Test Plan

Deployed on http://653cb211876d9041c5b7.shardul.tech/ The vonage hook is working properly with the endpoint.

Related PRs and Issues

This is related to Issue #199

Have you read the Contributing Guidelines on issues?

Yes