Prerendered pages occupy multiple routes on Vercel

[Rich-Harris]

Describe the bug

Of these three URLs...

• https://kit.svelte.dev/docs/introduction
• https://kit.svelte.dev/docs/introduction/
• https://kit.svelte.dev/docs/introduction/index.html

...the second and third should redirect to the first. The Vercel adapter should generate a route manifest that cleans the URLs and respects the trailingSlash option.

Reproduction

See links above

Logs

No response

System Info

System:
    OS: macOS 12.0.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 89.98 MB / 32.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.13.1 - ~/.nvm/versions/node/v16.13.1/bin/node
    npm: 8.1.2 - ~/.nvm/versions/node/v16.13.1/bin/npm
  Browsers:
    Chrome: 98.0.4758.80
    Firefox: 96.0.3
    Safari: 15.1
  npmPackages:
    @sveltejs/vite-plugin-svelte: ^1.0.0-next.32 => 1.0.0-next.32 
    svelte: ^3.44.2 => 3.44.2 
    vite: ^2.8.0 => 2.8.0

Severity

annoyance

Additional Information

No response