add OpenCL examples

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and how to leverage better the AMD GPUs

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Will try to adapt examples in a batch from:

• https://github.com/NAG-DevOps/OpenCL-examples
• https://github.com/NAG-DevOps/OpenCL-Tutorials
  with a sample job script to compile and run these.

[smokhov]

• https://github.com/FlorentFlament/amd-gpu-benchmark