docs: Add reference documentation for plugin

[euanh]

Motivation

Reference documentation, such as manual pages, complements getting started guides and tutorials by explaining a tool's interface and options in one place.

The build-container-image command plugin is the main user-facing tool in the project, so users will benefit from having reference documentation for it, available from the main documentation site.

At present, containertool will mostly be used through the plugin, which is a thin wrapper which calls containertool as a helper. Documenting containertool as a separate tool might be confusing. It has command line help for those who need to use it directly, and as the plugin is largely a wrapper its reference documentation also explains most of containertool's options.

Modifications

• Rewrite the containertool manual page for the build-container-image plugin.
• Add a Reference section to the curation, linking to the plugin manual page.

Result

Users have access to reference documentation which explains the interface and options of the build-container-image command plugin.

Test Plan

All existing tests continue to pass.

[heckj]

I'm guessing you created this by hand vs. using the generator command plug in swift argument parser? (I suspect by hand, as I don't think the plugin uses term lists unless you used the most recent build where I just added it)

The term lists are a great touch here!

[euanh]

Yes, I did this by hand. I started with the help output for containertool and adapted it, because the plugin's own help text is quite limited.

I don't think it's currently possible to generate help for a plugin itself because plugins can't use swift-argument-parser.