feat: initial support for command aliases

[nexdrew]

Allows a command to have aliases if given as an array, e.g.

.command(['start', 'run', 'go'], 'Start the app', builder, handler)

The first element in the array is treated as the canonical command, which supports positional args; the remaining elements are considered aliases. Aliases inherit their positional args from the canonical command and, thus, any positional args defined for an alias are ignored.

For example, all of the following are equivalent and only the <name> required positional arg will be parsed/validated:

.command(['hi <name>', 'hello'], 'Say hi', builder, handler)
.command(['hi <name>', 'hello <name>'], 'Say hi', builder, handler)
.command(['hi <name>', 'hello <someone> [others..]'], 'Say hi', builder, handler)

For help text, command aliases are displayed in a new right-aligned column after the canonical command and description, e.g.

$ node test.js help
Commands:
  start      Start the app                                    [aliases: go, run]
  hi <name>  Say hi                                             [aliases: hello]

Options:
  --help  Show help                                                    [boolean]

TODO:

• Tests
• Add "aliases:" to all locales Will create a new issue for this
• Docs

[bcoe]

I like this implementation of aliases 👍 it's nice to see cliui being dusted off.

[bcoe]

@nexdrew for the locale files; feel free to open an issue and not let this block landing this feature.

[nexdrew]

This should be ready for final review. Added the ability for command modules to export an aliases property so they don't have to use an array for the command property, because why not.

@bcoe @maxrimue Let me know what you think.

[maxrimue]

LGTM, nice work 👍

We should probably open a new issue to call for translations of aliases once this PR is merged. Btw, the German translation would be Aliase, maybe you can implement this right into this PR @nexdrew?
I think we also still need to call for translations for Did you mean?, could do this in the same issue.

[nexdrew]

Oh good point! Thanks @maxrimue, I'll do that.

[bcoe]

This is wonderful @nexdrew, I'm hoping to take on default commands tomorrow using this as a jumping off point.