Create dotnet new template for NuGet library projects

- Allow setting LangVersion (default to 9.0)
- Enable warnings as errors on all projects (consider Directory.Build.props)
- Add IntelliTect analyzer library (allow setting version in template)
- Add in unit test project (slight preference to xUnit)
- README.md
- Should have a single unit test that go against the library passes (Hello world level)
- Enable flag to create nuget package on every build.

The contents for the template should live in a new folder at the root of the repo named `templates`.
The folder for this template should be called `IntelliTectClassLibrary`

Name of the template: IntelliTect Class Library
Short Name: itl-classlib
Tags: IntelliTect/Library