Add public API for escaping command line arguments

[madelson]

MedallionShell auto-escapes, but sometimes you need nested escaping (e. g. https://github.com/madelson/MedallionShell/issues/68#issuecomment-603876613).

API might look like:

class Command
{
   static string EscapeArguments(IEnumerable<string> args, OSPlatform? platform = null)
}

One downside to this is that people might get confused and think they need to call this all the time when 99% of the time they don't need it.