Changes:
- added support for using cookies, to be able to retrieve age restricted videos
- API usage: `YouTubeTranscriptApi.get_transcript(video_id, cookies='/path/to/your/cookies.txt')`
- CLI usage: `youtube_transcript_api <first_video_id> <second_video_id> --cookies /path/to/your/cookies.txt
`
Thanks to danielcliu for the contribution!