CLI should show version and package name of command it executes
Currently, the user runs the CLI with the -v option or version command, the CLI shows the version of the CLI. First, it's not clear that this is the version of the CLI only. Second, it doesn't show the CLI of the generator package.
In addition to the CLI version (which should be explicitly marked), the CLI should output the version of the package that corresponds to the command it's going to execute. For instance, for the generate command, the CLI should show the version (and package name) of the generator.
Example:
$ antora -v
CLI: 3.0.0-alpha.1
@antora/site-generator-default: 3.0.0-alpha.1
Showing the version of the generator can help the user troubleshoot when different versions of the CLI and generator are installed, or the user is using a custom generator.
Right now, the only executable command is generate, so the CLI can assume this. But in the future, the CLI should show the version of whatever package it's going to execute.