`/favicon.ico` cannot be served by endpoint

[bakkerthehacker]

Describe the bug

Endpoints are not able to process any requests made to /favicon.ico. An endpoint file named /favicon.ico.js does run at all and a 404 is returned instead. While static assets can be served on the /favicon.ico path, the endpoint cannot; this limits /favicon.ico severely for anything more than one file (or some file swapping).

Adjustments can be made with rel="icon" to use a different path, but /favicon.ico is a well known path and should be supported with endpoints.

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-rk12yp?file=src/routes/favicon.ico.js
https://github.com/bakkerthehacker/sveltejs-kit-template-default-rk12yp (empty, syncing from stackblitz not working)

/favicon.ico.js and /favicon2.ico.js both have 302 redirects to /todos

localhost:3000/favicon2.ico -> 302 redirects to /todos as expected

localhost:3000/favicon.ico -> 404

Logs

No response

System Info

envinfo doesnt run with `--system` on stackblitz

❯ npx envinfo --binaries --browsers --npmPackages "{svelte,@sveltejs/*,vite}"
success Install finished in 0.399s


  Binaries:
    Node: 16.14.2 - /usr/local/bin/node
    Yarn: 1.22.10 - /bin/yarn
    npm: 7.17.0 - /bin/npm
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.42 
    @sveltejs/kit: next => 1.0.0-next.330 
    svelte: ^3.46.0 => 3.48.0

Severity

serious, but I can work around it

Additional Information

See this comment on the previous favicon.ico PR: #3559 (comment)