Restore acknowledgments and improve Windows install docs

[jsilverdev]

Summary

• restore the original acknowledgments for Lissy93 and KevinNitro dotfiles
• change the Windows quick-install instructions to start from Windows PowerShell 5.1
• use Invoke-WebRequest -UseBasicParsing to download bootstrap.cmd
• launch bootstrap.cmd explicitly through cmd.exe
• clarify that PowerShell 5.1 is only the download/launch shell and the bootstrap provisions PowerShell 7 as needed