Streaming download

[MForster]

ModPortalClient::download_mod currently returns a Result<Bytes>. We probably want a version that doesn't store the whole ZIP file in memory. Or maybe a version that goes straight to a file?

[Builditluc]

We could use the bytes_stream (EDIT: docs) function in the reqwest library to convert the response into a stream of bytes and then download each chunk directly into a newly generated file (the path of the file would be given to download_mod). I can create a PR if that sounds good

[MForster]

That would be great!