Support yml extension

[gbonnefille]

The .yml is a common variation of the .yaml extension.

[rykov]

@gbonnefille Looks good, however, as they are private, I don't see a reason to keep both walkFilesByExts and walkFilesByExt. So why not do something like this to avoid walking the filesystem multiple times:

func (fs *Fs) walkFilesByExts(dir string, exts []string, walkFn func(path, key string, fi os.FileInfo, err error)) error {
  return afero.Walk(fs, dir, func(path string, fi os.FileInfo, err error) error {
    if err != nil || fi.IsDir() {
      return nil
    }

    pathExt := filepath.Ext(path)
    if !slices.Contains(exts, pathExt) {
      return nil
    }

    // Remove dir prefix and extension
    key, _ := filepath.Rel(dir, path)
    key = key[:len(key)-len(pathExt)]
    walkFn(path, key, fi, nil)
    return nil
  })
}

[gbonnefille]

I applied your suggestion