Add alternate methods for installing on Windows

I'm doing some work with Windows Docker containers and I'm having trouble installing Just.

The official image that I'm working with ([microsoft-dotnet-framework-sdk - Official Image | Docker Hub](https://hub.docker.com/_/microsoft-dotnet-framework-sdk/)) doesn't include [WinGet](https://github.com/microsoft/winget-cli) or any other package manager, so out of the box none of the [packages in the Just Programmer's Manual](https://just.systems/man/en/chapter_4.html) will work.

I've tried installing [Scoop](https://scoop.sh/) while in an interactive session, but since I don't have an elevated prompt the install fails.

I was able to find an installer for `winget`, but it clocked in at around 240MB, which is impractical.

There's no `sh` or `bash` on the image, so installing using https://just.systems/install.sh (from [Pre-Built Binaries - Just Programmer's Manual](https://just.systems/man/en/chapter_5.html)) isn't an option.

I note that this sort of thing has come up in the past in #446 with no long term resolution.

One idea is to use the `dotnet` command line tool (available on the image) to install a wrapper around Just that's a [.NET tool](https://learn.microsoft.com/en-us/dotnet/core/tools/global-tools-how-to-create). Then installation would be as simple as `dotnet install just`.

Read the Pre-Built Binaries chapter and the linked installation methods, then review the history of issue #446. Investigate installation options available in the Microsoft .NET Framework SDK Windows container, including the proposed .NET tool approach. Done means identifying and documenting or implementing a practical installation method that works without a package manager, shell, or elevated prompt.

Written by the indexing model from the issue text.