add option "charset" to support other language

add option "charset" to support double-byte encoding language,
this can fix chinese word erro show.
```
    options = utils.extend(options || {}, {
        base64: false,
        checkCRC32: false,
        optimizedBinaryString: false,
        createFolders: false,
        decodeFileName: utf8.utf8decode,
        charset:'gbk'
    });
```

dist/jszip.js

@@ -1106,7 +1106,8 @@ module.exports = function (data, options) {
         checkCRC32: false,
         optimizedBinaryString: false,
         createFolders: false,
-        decodeFileName: utf8.utf8decode
+        decodeFileName: utf8.utf8decode,
+        //charset:'gbk'
     });
 
     if (nodejsUtils.isNode && nodejsUtils.isStream(data)) {
@@ -4026,7 +4027,46 @@ ZipEntry.prototype = {
     /**
      * Apply an UTF8 transformation if needed.
      */
+
+    decode:function(u8,i){
+        i = i||0;
+        if(this.loadOptions.charset&&this.loadOptions.charset!='utf8'){
+          for(;i<u8.byteLength;i++){
+            if(u8[i]>127){
+              //not a ascii
+              let utf8 = false;
+                var k=0;
+                for(var j=1;j<u8[i].toString(2).split('0')[0].length;j++){
+                  if(u8[i+j]>>6==2){
+                    //10xxxxxx
+                    k+=1;
+                  }
+                }
+                if(k>0&&k==j-1&&u8[i+j]>>6!=2){
+                    if(k==1){
+                      //double byte
+                      //some gbk will erro
+                      return this.decode(u8,j);
+                    }else{
+                      utf8 = true;
+                    }
+                }
+              if(utf8===false)return new TextDecoder(this.loadOptions.charset).decode(u8);
+              break;
+            }
+          }
+        }
+        return new TextDecoder().decode(u8);
+    },
     handleUTF8: function() {
+        if(this.loadOptions.decodeFileName == utf8.utf8decode){
+            this.fileNameStr = this.decode(this.fileName);
+            this.fileCommentStr = this.decode(this.fileComment);
+        }else{
+            this.fileNameStr = utf8.utf8decode(this.fileName);
+            this.fileCommentStr = utf8.utf8decode(this.fileComment);
+        }
+        return;
         var decodeParamType = support.uint8array ? "uint8array" : "array";
         if (this.useUTF8()) {
             this.fileNameStr = utf8.utf8decode(this.fileName);
@@ -11580,4 +11620,4 @@ module.exports = ZStream;
 
 }).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
 },{}]},{},[10])(10)
-});
+});