Add site script for use with site designs.

• command: spo sitescript add -t|--title <title> -d|--description [description] -c|--content <content>
• title: Site script title
• description: Site script description (optional)
• content: JSON string containing the site script
• requires connection to the SharePoint tenant admin site

For more information see the Add-SPOSiteScript cmdlet in the November release of the SPO PowerShell.