Use the proper Accept header to reduce the amount of metadata needed to sync

[decko]

Is your feature request related to a problem? Please describe.
When using the proper header, the amount of metadata needed to download obtain the package information is
drastically reduced, with huge savings, some time 70%.

Describe the solution you'd like
To inject the Accept: application/vnd.npm.install-v1+json to any request to the NPM Registry.