feat(client): add VPLink and RouterLink

[Mister-Hope]

@vuepress/client

• new useResolvedRoute composables (with redirects support)

two replacement for <RouterLink> in vue-router:

• new <VPLink> component, do not resolve any route during initialization.
• new <RouterLink> component, handling redirects and reduce router.resolve cost comparing with official <RouterLink> and active state with vp-active

@vuepress/markdown

• support and use <VPLink> by default for links plugin

@vuepress/shared

• new inferRoutePath function to avoid possible redirect matching that needs to call router.resolve again

Documentation

All related api docs update

Performance

( under 6x slowdown mocking withofficial docs)

Original:

Before:

After:

Adding 1000 pages on official docs:

  // all pages have been loaded after initialization
  onInitialized: async (app) => {
    for (let i = 1; i < 1000; i++) {
      const homepage = await createPage(app, {
        path: `/${i}`,
        // set frontmatter
        frontmatter: {
          layout: 'Layout',
        },
        // set markdown content
        content: `\
# Welcome to ${app.options.title}

This is page ${i}
`,
      })
      // add it to `app.pages`
      app.pages.push(homepage)
    }
  },

Before:

After:

[meteorlxy]

So the new <RouterLink> is not actually in use, right?

Is it possible to get rid of both new and old <RouterLink>? If so, I think it's better to use <VPLink> to replace the <RouterLink> totally.

My concern is to reduce user's confusion about the three different link components.

[Mister-Hope]

[Mister-Hope]

I think we can stop providing the official router-link and use ours instead. But that could be a breaking change.

The router link component should be kept as we do care about active state and the exact href location sometimes.

With this, users should import the real routerlink and overide ours if they do want the official one