Document comparison is opposite from expected order

Per the readme, the expected PowerShell call syntax is as follows:
`powershell -File Diff-Word.ps1 oldfile.docx newfile.docx`
However, the result is the opposite: Word treats `newfile` as the original and `oldfile` as the updated. This is because the Word command `Document.Compare` expects the syntax `NewDocument.Compare(OldDocument, ...)` but the PowerShell script uses `OldDocument.Compare(NewDocument, ...)` which explains the inverted result in Word. Unfortunately the correct syntax is very unclear in the [Microsoft documentation](https://docs.microsoft.com/en-us/dotnet/api/microsoft.office.tools.word.document.compare) so the confusion is quite understandable. However, the PowerShell script should align with the correct use of the Word command.