fix cordova file-transfer plugin - upload method

same as in issue #5435 for download method

cordova/cordova-tests.ts

@@ -192,7 +192,7 @@ file.upload('cdvfile://localhost/persistent/path/to/downloads/',
             console.error('Failed with exception ' + err.exception);
         }
     },
-    { headers: null, httpMethod: "PUT" },
+    { headers: {"X-Email": "user@mail.com", 'X-Token': "asdf3w234"}, httpMethod: "PUT" },
     true);
 
 file.abort();

cordova/plugins/FileTransfer.d.ts

@@ -93,7 +93,7 @@ interface FileUploadOptions {
     /** Whether to upload the data in chunked streaming mode. Defaults to true. */
     chunkedMode?: boolean;
     /** A map of header name/header values. Use an array to specify more than one value. */
-    headers?: Object[];
+    headers?: Object;
 }
 
 /** Optional parameters for download method. */