Feature request: streaming file uploads

[ddevault]

gqlgen's file upload support presently depends on http.Request.FormFile, which reads out the entire file into a temporary location, either RAM or on disk. This is more convenient to work with, but for large files, this can introduce a substantial overhead. Users sensitive to these constraints may prefer to use a streaming approach via http.Request.MultipartReader, which should be facilitated by gqlgen.