add notes about gzip encoded content to haxe.http.HttpBase

[nulld]

Found, that haxe.Http don't handle gzip encoded responses. So, in onData callback string is messy if response Content-Encoding is gzip. IMHO, it have to be mentioned in docs somehow. It can save a lot of time to those who will face this problem.

My solution to handle this:

class Main {
    public static function main() {
        
        var r = new haxe.Http("http://cf.gcdn.co/cf/145/assets_remote/assetsRepository.json");
        r.onStatus = s -> trace(r.responseHeaders);
        r.onBytes = bytes -> {
            trace(r.responseHeaders["Content-Encoding"]);
            if (r.responseHeaders["Content-Encoding"] == "gzip") {
                var reader = new format.gz.Reader(new haxe.io.BytesInput(bytes, 0, bytes.length));
                var s = reader.read();
                trace(s);
            }
        };
    }
}

Btw, we can link cookbok with similair solution to docs.

P.S: it works but only for sys . For nodejs target there are no responseHeaders property in haxe.Http so haven't idea how to handle it.