Hello,

This PR adds support for using hub as an NPM proxy for actual client APIs.

You can use it as a registry URL:

npm config set registry http://localhost:6587/npm/npmjs

Or as a scoped registry:

npm config set @my-scope:registry http://localhost:6587/npm/npmjs

Alternatively, you can add it to your .npmrc file:

registry=http://localhost:6587/npm/npmjs

Additionally, this PR includes:

• Added the modernize linter to .golangci.yml
• Refactored code to use any instead of interface{} in accordance with the modernize linter
• Improved handling of the X-Cache-Status header
• Logging of the X-Cache-Status header for improved request visibility.