platyPS help markdown can be found here: /docs/help.
To generate the external help use New-ExternalHelp
:
Update-MarkdownHelp -Path "docs/help/en-US"
New-ExternalHelp -Path "docs/help/en-US" -OutputPath "Evergreen/en-US" -Encoding ([System.Text.Encoding]::UTF8) -Force
Update-MarkdownHelpModule -Path "docs/help/en-US"