Add a configuration option for Unix vs. Windows-style line endings

[DaRosenberg]

We are implementing TypeGen in project developed primarily on macOS and Linux. Our linters, IDEs and Git repolitory are consequently all configured for Unix-style line endings (LF only). However, TypeGen currently seems hard-coded to output TypeScript files with Windows-style line endings (CRLF) even when run on a Unix-based operating system, which causes some difficulty for us.

Would it be possible to add a configuration option for this so we can add something like this to our tgconfig.json file?

{
    "lineEndings": "auto" | "windows" | "unix"
}

Where "windows" would be the default for now, in order to avoid a breaking change (might consider changing the default to "auto" in the next major version), and where "auto" would use System.Environment.NewLine to do what's expected on the current platform.