Update README.md

fix the example error occur at `vid.Download(vid.Formats[0], file)`:

**vid.Download undefined, (type *ytdl.VideoInfo has no field or method Download)**

README.md

@@ -18,17 +18,22 @@ import (
  "os"
 
  "github.com/rylio/ytdl"
+ "github.com/rs/zerolog/log"
 )
 
 func main() {
- vid, err := ytdl.GetVideoInfo("https://www.youtube.com/watch?v=WkVvG4QTO9M")
+ client := ytdl.Client{
+ HTTPClient: http.DefaultClient,
+ Logger: log.Logger,
+ }
+ vid, err := client.GetVideoInfo("https://www.youtube.com/watch?v=WkVvG4QTO9M")
  if err != nil {
  fmt.Println("Failed to get video info")
  return
  }
  file, _ := os.Create(vid.Title + ".mp4")
  defer file.Close()
- vid.Download(vid.Formats[0], file)
+ client.Download(vid, vid.Formats[0], file)
 }
 
 ```