[REQ] Provide templating authoring details in config-help or generate CLI command (or subcommands of generate)

Is your feature request related to a problem? Please describe.

Yes. The barrier to entry for authoring templates or custom generators should be minimized.

Describe the solution you'd like

config-help should provide some options for displaying more than CLI-only generation flags.

Examples:

• --authoring => could provide the embeddedTemplateDir as this isn't always the same as the generator name
• --extensions => could provide a list of vendor extensions for the generator
• --supporting-files => could provide a list of the supporting files.
• --features => could list the features supported by the generator (OAuth, JSON/XML, API Key, etc)

Describe alternatives you've considered

We could create a new CLI command, but that seems to add little value over one or more additional switches.

Additional context

I think any additional information should be hidden by default. That is, authoring and extension information shouldn't display when config-help is called for a generator without the additional switches. This is because some of our generators have a ton of options, and there's no need to crowd the terminal output.

The --supporting-files might be non-trivial because many generators conditionally add supporting files based on CLI options passed to the generator. I think we would need to update generators to "register" supporting files and associate them to the options which would lead to those files being generated.

The generated output could eventually be used to generate parts of our documentation (see #1770).