Allow .nuxtignore files within folders

[snapwich]

What problem does this feature solve?

Currently the Nuxt documentation refers to .gitignore files for an example for how to use .nuxtignore. However, .gitignore allows the files to be placed in various directories and ignore relative file paths from that directory. I think this would be a convenient feature to mirror in Nuxt with .nuxtignore.

What does the proposed changes look like?

example of how to ignore a file with existing functionality vs with multi-directory .nuxtignore

// /.nuxtignore pages/blog/2019/01-01-some-blog-post/ignoredfile.js

// /pages/blog/2019/01-01-some-blog-post/.nuxtignore ./ignoredfile.js

_{This feature request is available on Nuxt community (#c9309)}