PlatyPS default values should not get uppercased

This brings problems with cross-platform documentation using e.g. lowercase-only folders.

Should be fixed in PlatyPS as there is no way we can know what the original casing was.

> A good example is [this default value](https://docusaurus-powershell.netlify.com/docs/CmdLets/New-DocusaurusHelp#-outputfolder) for `OutputFolder`, should be lowercase.