lib: gbk decoder is gb18030 decoder per spec

PR-URL: #61099
Refs: https://encoding.spec.whatwg.org/#gbk-decoder
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: ChALkeR

lib/internal/encoding.js

@@ -431,7 +431,9 @@ function makeTextDecoderICU() {
 
     #prepareConverter() {
       if (this[kHandle] !== undefined) return;
-      const handle = getConverter(this[kEncoding], this[kFlags]);
+      let icuEncoding = this[kEncoding];
+      if (icuEncoding === 'gbk') icuEncoding = 'gb18030'; // 10.1.1. GBK's decoder is gb18030's decoder
+      const handle = getConverter(icuEncoding, this[kFlags]);
       if (handle === undefined)
         throw new ERR_ENCODING_NOT_SUPPORTED(this[kEncoding]);
       this[kHandle] = handle;