registry: Add private field to prevent wasted HTTP requests

[suzuki-shunsuke]

Feature Overview

Add a boolean field private and if the field is true, aqua doesn't call HTTP requests to download assets and directly calls GitHub API.

Why is the feature needed?

Please explain the problem you want to solve.

This change prevents aqua from calling HTTP requests to download assets.
aqua can't download assets without GitHub Access Token, so the request is wasteful.

Does the feature include Breaking Changes?

No.

Example Code

command and configuration

$