docs: npm help json/global command on windows

[klm-turing]

On Windows, npm help json and npm help global attempt to display npm-json.html and npm-global.html files which leads to an error because these files have not been generated.

This pull request duplicates the package-json.md and folders.md files in order to generate these files and make the above-mentioned commands functional.

References

Closes: #7374

[klm-turing]

@wraithgar I had to update nav.yml file in order to pass check-nav.js test since I've also duplicated md files. Let me know if it is OK. Thank you

[lukekarrys]

Thanks for your work on this! I had to double-check but we don't actually want to add the aliases for the markdown docs. The markdown files are used in https://github.com/npm/documentation and get their own html redirects in that repo. It's not ideal to have these separate but there are many more html redirects in order to prevent breaking old urls, and those will never apply to the man or html pages (which are just used as a man page replacement on Windows).

[klm-turing]

You are welcome @lukekarrys. Thanks for your inputs and comments.

[mbtools]

thanks @klm-turing 👍