fix(docz-core): properly support node_modules for multiple file patterns

[axe312ger]

Description

Currently docs from node_modules are only supported when the src contains node_modules

This changes the code so that either src or any pattern can contain docs from node_modules

My config:

{
  resolve: `gatsby-theme-docz`,
  options: {
    files: [
      `src/components/mdx/**/docs/*.{md,markdown,mdx}`,
      `node_modules/@gatsby-mdx-suite/*/docs/*.{md,markdown,mdx}`,
      `../../node_modules/@gatsby-mdx-suite/*/docs/*.{md,markdown,mdx}`,
    ]
  },
}

[rakannimer]

Awesome ! I added a src check to avoid breaking any setups that relied on it.