Electron Releases

Description of Change

I stumbled upon this with an internal report that Sentry's Electron SDK was actually resetting the window from our own internal app.getAppMetrics() calls.

This info was buried deep in the CPUUsage.md structure doc, and not immediately discenerable from the API docs themselves.

This PR does a few things:

• Adds more detail on how the measurement intervals work in CPUUsage.md.
• Adds a brief note on using cumulatedCPUUsage to calculate CPU usage in a given window.
• Adds notes to process.getCPUUsage and app.getAppMetrics linking to CPUUsage.md.

cc @electron/docs

Checklist

• I have built and tested this change
• I have filled out the PR description
• I have reviewed and verified the changes
• relevant API documentation, tutorials, and examples are updated and follow the documentation style guide
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: none