Add a C++ CI/CD example
We should add a C++ CI example like we have done with others in https://gitlab.com/gitlab-examples. <details> i want to try CI/CD in gitlab, i can not find the C++ CI/CD example in the website(https://gitlab.com/help/ci/examples/README.md) when i read document![example](/uploads/60fa925d5819dd456c348880b5672076/example.png) who can help me or tell me where can i find the relate document thanks. </details>
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