doc: modernize and fix code examples in process.md

Checklist

• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

doc, process

• Replace var by const.
• Use console.error().
• Fix example file name mismatch (compare with the previous example description).
• Update output examples.
• Increase output readability (add a line break, remove an unnecessary duplicate word).