Add supported command sections to each package manager

Problem to solve

To help users understand how they can best use the package registry, we should be explicit in which CLI commands we support for each package manager. This can help prevent confusion on if something is a bug, or needs to be a new feature. This section may not be relevant if there is not a specific CLI tool with commands being used (for example generic packages or the publish portion of composer), but if no specific CLI tool is used, perhaps other options could be listed in an organized manner (such as curl options/params). We could also display any commands that have open issues for being implemented with a link to the issue.

Further details

• Composer
• Conan
• [-] Go Proxy
• Maven
• npm
• NuGet
• PyPI
• [-] Generic (does not apply, no client)
• RubyGems

Who can address the issue

Anyone in the package group or with expertise in the package registry.

Other links/references

Inspired by #323340 (comment 524150881)