doc: describe when stdout/err is sync
process.stdout, process.stderr, and console.log() and console.error() which use the process streams, are usually synchronous. Warn about this, and clearly describe the conditions under which they are synchronous.
Fix: https://github.com/nodejs/node/issues/10617
Checklist
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documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc,console,process