Improve mint output

[pixyzehn]

Just improved the output like this. I followed the way swift package command does as you can see.

---

Before

OVERVIEW: run and install Swift PM executables

USAGE: mint mint [subcommand]

OPTIONS:
  --version, -v
              Prints the current version of Mint
  --help      Display available options

SUBCOMMANDS:
  install     Installs a package. If the version is already installed no action will be taken
  list        Lists all the currently installed packages
  run         Installs and then runs a package
  uninstall   Uninstalls a package by name.
Use mint list to see all installed packages
  update      Updates a package even if it's already installed

After

OVERVIEW: Run and install Swift Package Manager executables

USAGE: mint [subcommand]

OPTIONS:
  --version, -v
              Print the current version of Mint
  --help      Display available options

SUBCOMMANDS:
  install     Install a package. If the version is already installed no action will be taken
  list        List all the currently installed packages
  run         Install and then run a package
  uninstall   Uninstall a package by name
  update      Update a package even if it's already installed

[yonaskolb]

Good catch, thanks @pixyzehn!