Lost content-length header fix

src/android/src/main/java/com/RNFetchBlob/RNFetchBlobBody.java

@@ -59,7 +59,12 @@ public RNFetchBlobBody(String taskId, RNFetchBlobReq.RequestType type, String ra
     public MediaType contentType() {
         return mime;
     }
-
+
+    @Override
+    public long contentLength() {
+        return contentLength;
+    }
+
     @Override
     public void writeTo(BufferedSink sink) throws IOException {