feat: allow spaces in CLI name for help output

[Rugvip]

Hello @privatenumber 👋, same context as privatenumber/type-flag#52

I'm wondering if this is a change you're open to. It relaxes the restriction on top-level CLI naming to allow spaces within the name. Our use-case is separation of the command hierarchy and individual definitions. The command implementations only parse the args provided to the command using cleye, rather than the full process argv slice. There's a different layer that handles the command routing.

The benefit of this change is that we can rely on the built-in usage generation in cleye, rather than needing to redefine it. For example, the following:

cli({
  help: { description: ..., usage: 'my-cli repo test [flags...] <path>' },
  parameters: ['<path>'],
  flags: ...,
}, undefined, args)

Can be switched to this:

cli({
  name: 'my-cli repo test',
  help: { description: ... },
  parameters: ['<path>'],
  flags: ...,
}, undefined, args) // side note - open to an (options, args) overload? 😉 

I was about to add a condition that restricts this to only be allowed if the commands option is not present, but realized that it might still be useful to allow this at the top level, but keep the restriction within the commands of course.