doc: add inspector usage example
Add a simple example showing how to use the inspector API to access the CPU profiler.
Checklist
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documentation is changed or added -
commit message follows commit guidelines
CI-light: https://ci.nodejs.org/view/Node.js/job/node-test-commit-light/362/ https://ci.nodejs.org/view/Node.js/job/node-test-commit-light/365/