usage function

void usage()

Implementation

void usage() {
  stdout.writeln('Usage:'
      '\nenv-gen <cmd> [flags]'
      '\ncmd'
      '\n\tinitialize\t\tcreates template env file and corresponding directories'
      '\n\t<environment>\t\tstring representing an environment from the env.json'
      '\n\thelp\t\t\toutputs this usage help'
      '\nflags'
      '\n\t-v\t\t\tturns on verbose logs'
      '\n\t-f <path>\t\tdefine alternate env.json file to use'
      '\n\t-e\t\tuse to output an additional .env file'
      '\n\t-o <path>\t\tdefine alternate output filepath for env.dart'
      '\n\t-h\t\t\toutputs this usage help');
}