Add windowsVerbatimArguments docs for child_process.spawn

This resurrects https://github.com/nodejs/node-v0.x-archive/pull/4259.

I changed a bit of the documentation to more closely mirror the docs found in the header http://docs.libuv.org/en/v1.x/process.html by taking the wording from https://nikhilm.github.io/uvbook/processes.html

Checklist

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

Affected core subsystem(s)

doc