Add RootModule name to manifest

[COV-Steve]

When importing the FolioClient module into my PowerShell session, the commands were not exported.

PS> Import-Module FolioClient
PS> Get-Module -Name FolioClient

ModuleType Version    PreRelease Name                                ExportedCommands
---------- -------    ---------- ----                                ----------------
Manifest   0.0.3                 FolioClient

Information I found online pointed to needing to fill in the RootModule name in the manifest, which I found to be commented out and empty in the current version.

Following that minor edit, importing the module successfully loaded the commands.

PS> Import-Module FolioClient
PS> Get-Module -Name FolioClient

ModuleType Version    PreRelease Name                                ExportedCommands
---------- -------    ---------- ----                                ----------------
Script     0.0.3                 FolioClient                         {Get-FolioClient, Get-FolioRecordIdsByQuery, Get-…