Change preview to work on git-bash as well, not just Powershell and cmd.exe

[gortok]

I'm really not sure if this is a Statiq.Web problem or a .NET Core problem; but on .NET 5; when I try to run dotnet run -- preview for a Statiq.Web project, I get the following error at the bottom of the output:

Error: The handle is invalid.

and the terminal exits the preview process for Statiq.Web:

I haven't tested it on WSL yet, though I'll report back when I do. I'm going off of a hunch that it's just a problem that would affect cygwin and git-bash; but I'll see.

[daveaglick]

I never thought to try under mingw - thanks for being a guinea pig :). Off the top of my head I'll guess it's a socket issue with the preview server, like maybe it's not able (or allowed) to open a socket. Should be easy enough to track down by attaching if I can repro locally.