* refactoring-1 introduced pipelines and abstracted download process.go in Downloader interface * migrated to boltdb from sqlite + session files * refactoring: config struct & pipelines * added js runtime for yt-dlp * updated dockerfile * added external js runtime, metadata scraping refactor * updated Dockerfile * fixed env propagation in docker * updated package name to v4 * updated readme and cd
supported modifiers are --playlist-start, --playlist-end, --playlist-reverse, --max-downloads