Create new cmdlets for creating Cab/Zip files for updateable help

[sdwheeler]

Summary of the new feature / enhancement

Need a cmdlet to replace New-ExternalHelpCab from platyPS 0.14.

Proposed technical implementation details (optional)

This needs to be cross-platform, where the CAB step is skipped on non-Windows platforms. Suggest using existing script-based cmdlet and tweaking it.

• Detect OS and skip as necessary
• Write verbose/warning about skipping
• Document behavior