Feature request

What problem does this feature solve?

Sites with many pages don't want to prefetch all pages. For example, a site with 1,000+ pages may want to prefetch no pages, or a small selection of main pages.

What does the proposed API look like?

In .vuepress/config.js add an option prefetch which defaults to true but can be changed to false to not prefetch any pages, or an array of pages.

module.exports = {
  // To not do any prefetching of pages
  prefetch: false,
  // Or to prefetch a selection of main pages
  prefetch: [
    '/about',
    '/faq',
    '/contact'  
  ]
}

How should this be implemented in your opinion?

Are you willing to work on this yourself?**