DOCSP-61800: CPP Getting Started

[tmcneil-mdb]

Summary | JIRA

Adds the C++ Get Started sample application under cpp/hello-world, mirroring the existing node/hello-world sample. The app connects to a MongoDB deployment using the connection string in the MONGODB_URI environment variable, seeds a few sample product documents into the get_started.products collection, then queries and prints one of them.

Changes:

• cpp/hello-world/main.cpp — sample application
• cpp/hello-world/CMakeLists.txt — targets the MongoDB C++ Driver (mongocxx) 3.10+
• cpp/hello-world/README.md — setup and run instructions
• cpp/hello-world/.gitignore — ignores build artifacts
• Added the C++ entry to the root README

This is the sample referenced by the C++ Get Started docs page link