Add Export-JS7InventoryFolder cmdlet to JS7 PowerShell Module for exporting folders

Current Behavior:

• When exporting the configuration from the GUI, there are two export type options: "Individual Objects" and "Folders." However, the available API in PowerShell, Export-JS7InventoryItem, uses the API call /joc/api/inventory/export. The PowerShell API call for Export-JS7InventoryFolder is missing, which is needed for the "Folders" export type.

Desired Behavior:

• In PowerShell, an Export-JS7InventoryFolder API should be added for the "Folders" export type. This API should call the /joc/api/inventory/export/folder endpoint.
• Version v2.0.21 of the JS7 PowerShell is available from https://github.com/sos-berlin/js7-cli-powershell/releases/tag/v.2.0.21