Willing to add a File publisher

[igrishaev]

First of all, thanks for the library! I've been happily using it after switching from clj-http. It's a part of our S3 internal client.

One thing I've noticed is, it looks like the convert-body-publisher function doesn't take into account a case when the body is a File object. The HttpRequest.BodyPublishers class has a static method to handle files: . ofFile(Path path). This is a good case for s3 because most often, we upload File objects there.

My question is, will you accept my PR if I extend the convert-body-publisher function with something like:

...
(instance? java.io.File body)
(HttpRequest$BodyPublishers/ofFile (.getPath body))

UPD: https://github.com/schmee/java-http-clj/pull/11