Added feature to support POST method when download is true

Added new config property named downloadRequestBody

papaparse.js

@@ -642,7 +642,7 @@ License: MIT
 				xhr.onerror = bindFunction(this._chunkError, this);
 			}
 
-			xhr.open('GET', this._input, !IS_WORKER);
+			xhr.open(this._config.downloadRequestBody ? 'POST' : 'GET', this._input, !IS_WORKER);
 			// Headers can only be set when once the request state is OPENED
 			if (this._config.downloadRequestHeaders)
 			{
@@ -661,7 +661,7 @@ License: MIT
 			}
 
 			try {
-				xhr.send();
+				xhr.send(this._config.downloadRequestBody);
 			}
 			catch (err) {
 				this._chunkError(err.message);