✔︎ sandbox
✔︎ extractQualities(from:) - throw instead of return optional
✔︎ don't sign all YouTube links, just the selected quality
✔︎ UGE - expand HLS qualities and don't list related content
✔︎ XUDownloadCenter - deprecate optional URL
✔︎ subtitle download on a separate thread -> XUDownloadProgress includes progress string
	✔︎ download = 75%
	✔︎ postprocessing = 20%
	✔︎ subtitle download = 5%
✔︎ better loading progress -> make XUURLToLoad public and display them
✔︎ better (immediate) cancellation -> XUDownloadCenter.cancellAllOperationsAndInvalidate()
✔︎ accurate ETA after pausing download
✔︎ custom postprocessing (shell script)
✔︎ use GET with a custom delegation to stop the load after response instead of HEAD (DOWNIE-25747)
✔︎ save metadata into JSON/XML file
✔︎ option to turn on/off external metadata file
✔︎ custom file name
✔︎ UGE history
✔︎ UGE favorites
⨯ Safari content blocker that delegates DMG, zip, MP4, etc. files to Downie
✔︎ Priority flags
✔︎ .downie part bundles
✔︎ menu bar only
✔︎ requires Permute 3
✔︎ option to force MP4


// Post 4.0
✔︎ custom site processing
- speed throttling
- quality - automatic identifier
- resume between launches
