addoption "charset" to decode filename

[nenge123]

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'
    });

[nenge123]

      decode:function(u8,i){
        i = i||0;
        var charset = this.loadOptions.charset;
        if(charset&&charset!='utf8'){
          for(;i<u8.byteLength;i++){
            if(u8[i]>127){
              //not a ascii
              var 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&&charset=='gbk'){
                      //double byte
                      //some gbk will erro
                      //return this.decode(u8,j);
                    }else{
                      utf8 = true;
                    }
                }
              if(utf8===false)return new TextDecoder(charset).decode(u8);
              break;
            }
          }
        }
        return new TextDecoder().decode(u8);
      },
      handleUTF8: function() {
          var charset = this.loadOptions.charset,
              utf8decode = utf8.utf8decode,
              decode = this.loadOptions.decodeFileName||utf8decode;
          if(charset&&'TextDecoder' in window&&'Uint8Array' in window){
            this.fileNameStr = this.decode(this.fileName);
            this.fileCommentStr = this.decode(this.fileComment);
          }else if(this.useUTF8()){
            this.fileNameStr = utf8decode(this.fileName);
            this.fileCommentStr = utf8decode(this.fileComment);
          }else{
            var decodeParamType = support.uint8array ? "uint8array" : "array";
            var upath = this.findExtraFieldUnicodePath();
            if (upath !== null) {
                this.fileNameStr = upath;
            } else {
                // ASCII text or unsupported code page
                var fileNameByteArray =  utils.transformTo(decodeParamType, this.fileName);
                this.fileNameStr = decode(fileNameByteArray);
            }
            var ucomment = this.findExtraFieldUnicodeComment();
            if (ucomment !== null) {
                this.fileCommentStr = ucomment;
            } else {
                // ASCII text or unsupported code page
                var commentByteArray =  utils.transformTo(decodeParamType, this.fileComment);
                this.fileCommentStr = decode(commentByteArray);
            }
          }
      },

[Stuk]

Thanks for the PR! Does this only work for gbk encoding, or also others?

And a few thoughts/comments:

1. Could you merge main and fix the linting errors
2. Could you add comments to the new code to explain what is going on?
3. I think it might be best if utf8.js was renamed to maybe charset.js, and decode was moved there
4. Could you add some tests for this new code?

[nenge123]

Thanks for the PR! Does this only work for gbk encoding, or also others?

And a few thoughts/comments:

1. Could you merge main and fix the linting errors

2. Could you add comments to the new code to explain what is going on?

3. I think it might be best if utf8.js was renamed to maybe charset.js, and decode was moved there

4. Could you add some tests for this new code?

1. By coincidence, I compressed the list of file names encoded with gbk and utf8, and it was successfully decoded!

2. I didn't test other ansi codes such as Japanese and Korean. However, it is certain that at least it is more convenient than the original utf8 encoding, such as emoji.

3. There may be a problem. Ansi double-byte problem handling problem, because utf8 also has double bytes. Refer to k==1 &&charset="gbk" in decode, which means that if gbk is specified, then all double bytes are encoded as gbk, or continue to loop. Until you make sure it's not utf8.

4. I think ansyc ("text") decodes faster in this way, and utf8 files will not be garbled.