[HTML] YouTube RSS Feed & Thumbnail

* 유튜브(YouTube) RSS Feed 주소

# 채널(Channel)
https://www.youtube.com/feeds/videos.xml?channel_id=CHANNEL-ID

# 사용자(User)
https://www.youtube.com/feeds/videos.xml?user=USER-NAME

# 재생목록(Playlist)
https://www.youtube.com/feeds/videos.xml?playlist_id=PLAYLIST-NUMBER

* 썸네일(Thumbnail)

# Default
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/default.jpg

# Standard Definition
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/sddefault.jpg

# High Quality 
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/hqdefault.jpg

# Medium Quality
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/mqdefault.jpg

# Maximum Resolution
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/maxresdefault.jpg

# ETC
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/0.jpg
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/1.jpg
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/2.jpg
https://img.youtube.com/vi/YOUTUBE-VIDEO-ID/3.jpg