doc: missing API links in process markdown

[mscdex]

• Version: master, v7.7.0+
• Platform: n/a
• Subsystem: doc

The "A note on process I/O" section in the process.stdout description is missing link references at the bottom of the markdown for console.log() and console.error(), causing the links to not render correctly.

[sam-github]

I will fix.

[fhinkel]

Thanks!