• Add showMultiSelectDialog and showSingleSelectDialog to new
  cli_components library, as well as an example.
• Adds a package:cli_util/windows_compatibility.dart library which initially
  contains just the Win32AnsiStdin class. This can be used on Windows to get
  a stdin stream that forwards arrow keys and other special keys in the way
  that you'd expect, and converts then to ANSI escape sequences.
  • Note that this is not a full implementation, and only handles the events
    that are needed for the CLI components in this package.
• Increases min SDK constraint to ^3.7.0.