Resumable Uploads: Subsequent resources using `Content-Location`

[Acconut]

In https://github.com/httpwg/http-extensions/issues/2312 we discussed how a server could provide the client with access to information and resources that are generated based on the uploaded data. One solution that emerged was a Content-Location header the pointed to another resource, where the client could download data, fetch extracted information etc. This PR adds a small section explaining this possibility and its interaction with resumable uploads.

Closes #2312