Extract and respond with bytes instead of string

[cyqsimon]

Extracting the body with response.text() causes binary blobs to be erroneously escaped. For example:

$ PORT=8000 cargo run &
$ curl -o original https://github.com/cyqsimon/documented/archive/refs/tags/v0.2.0.tar.gz
$ curl -o proxied http://localhost:8000/https://github.com/cyqsimon/documented/archive/refs/tags/v0.2.0.tar.gz

# the two files should be the same but are not
$ ls -l original proxied
$ md5sums original proxied

By extracting the bytes instead, all kinds of files are correctly passed through.