fixed the doc of the decoder.

decoder may get also string, not just buffer - so rename it to chunk.

docs/docs.html

@@ -536,11 +536,11 @@ var csv = Papa.unparse({
 									<code>decoder</code>
 								</td>
 								<td>
-									A function which allows custom decoding for the buffer string.
+									A function which allows custom decoding of the chunk.
-									The function get Buffer and Encoding, and returns a string.
+									The function get Chunk (Buffer/string) and Encoding, and returns a string.
 									i.e assuming const iconv = require('iconv-lite'):
-									(buf , encoding) => {
+									(chunk , encoding) => {
-										if (iconv.encodingExists(encoding)) { return iconv.decode(buf, encoding) };
+										if (iconv.encodingExists(encoding)) { return iconv.decode(chunk, encoding) };
 										throw new TypeError('[ERR_UNKNOWN_ENCODING]', 'Unknown encoding: ' + encoding)	   
 									}							
 								</td>