W10_11langpack.ps1 [better] -

[Parameter(Mandatory=$false)] [switch]$IncludeHandwriting

Unlike consumer-grade language switching (which uses Settings > Time & Language), this script targets scenarios: w10_11langpack.ps1

If you are looking for the specific file download rather than the methodology, it is likely a script maintained by or a similar MVP (Most Valuable Professional). Time & Language)