msprites，媒体缩略图精灵，多缩略图缩略图 要求： 1. FFmpeg 2. ImageMagick Montage 脚步： 1. Extract images using ffmpeg. You can configure size of image and image rate per second(ips) 2. Convert Image in spirtesheet of grid ROWSxCOLS 3. Create a webvtt file of spriteshee