fix: npm.org now has a different way to request info about scoped packages

[GerHobbelt]

via the Npm-Scope header. See also https://docs.npmjs.com/misc/registry

Code fixed and works at least for a few of my own scoped packages.

[rarkins]

@GerHobbelt thanks for all your contributions. I was a little surprised to see this PR, as I also query scoped packages in my project renovate. I read the npm page, I'm not 100% sure this is the right way to do this, although I can see why it works. The page says:

If your project is scoped, this header will contain its scope.

It doesn't necessarily follow that the correct way to request any scoped package is to use that header - aren't they just warning that if the project you're working on is scoped then that scope will be transmitted to npm?

I wonder for instance if you were to include scope 'a' in the Npm-scope header but the URL was @b%2Fc then would it return @a/c or @b/c.

Anyway in short, I'd like to confirm that this way is preferred over the existing way, as I know the existing way works fine for now.

[GerHobbelt]

Ah, I did this because the existing way broke for me: npm rejected the requests.

(After GerHobbelt/jison#11 I changed to using scoped packages, e.g. @gerhobbelt/changelog. Invoking changelog on my changelog copy (@gerhobbelt/changelog) failed immediately, until I moved the code to this new header-based approach. I did test it on a few of these repos of mine but I DID NOT test it on other scoped packages, i.e. scopes done by others.)