Most package.json fields removed from environment in npm v7

[valentinoli]

Hello fellow Nuxt contributors and developers! I noticed that in npm 7, they have reduced environment variables provided to lifecycle scripts. This means some of the defaults used in this module do not work with npm 7. Notably:

• npm_package_description used in the Meta and Manifest modules as default for description
• npm_package_author_name used in the Meta module as default for author

However, npm_package_name is still provided.

In light of this change in npm 7, I suggest removing defaults altogether for these fields