Fix extract when fileName is a directory

[f111fei]

See https://github.com/thejoshwolfe/yauzl/blob/master/README.md

  zipfile.on("entry", function(entry) {
    if (/\/$/.test(entry.fileName)) {
      // directory file names end with '/'
      mkdirp(entry.fileName, function(err) {
        if (err) throw err;
        zipfile.readEntry();
      });
    } else {
      ......
    }
  };

If entry.fileName is a directory name, extracting will be failed.

Here is a test file.
https://github.com/f111fei/test-files/raw/master/test.zip

The case has 4 entries.

/
/1/
/1/2/
/1/2/README.md

[mention-bot]

By analyzing the blame information on this pull request, we identified @egamma and @joaomoreno to be potential reviewers

[joaomoreno]

@f111fei I took your suggestion from #8044 and started writing tests for zip: a11c9b2

The first (and only, so far) test tries to extract the file you appended to this PR. The test seemed to pass successfully... I then realised the file you provided didn't cause the issue. It needs to be a zip file containing an empty directory. I've updated the test and then it started failing.

[joaomoreno]

Your fix got close, but there was still the problem of opening the stream of an empty directory: the extract would never end. I've pushed another commit on top.

For some idiotic reason I failed to properly preserve history and ended up not merging this properly and did a rebase instead. You still appear as a committer, though: 74b8236

Thanks for your help! 🎆 Great job! 🍻