Document remote workstation setup

What does this Merge Request do and why?

Documents steps required to set up GDK on a remote workstation in GCE.

⚠ This is blocked by gitlab#213259 (closed) ⚠

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.