Fixed the lowercase option being applied by default even when unchecked in settings.

Added options page for customizable filename format using {artist}, {title}, {year}, {genre}, {album}, and {username} tokens, with lowercase option and live preview.

changelog:
- fixed a bug where client ID extraction failed due to SoundCloud's updated script format, preventing download button from appearing

changelog:
- rework button style to match new soundcloud ui

changelog:
- fixed a bug where download of songs with no artwork + user with no profile picture (which is the default fallback) did not work (e.g. https://soundcloud.com/lareena61030/laker-phreshboyswag-no-reason-elipropper)

changelog:
- fixed a bug where download of songs with no description did not work (closes https://github.com/nyo/scdl/issues/7)
- added support for `publisher_metadata` which is metadata entered by the person uploading the music (= more reliable)
- now uses `publisher_metadata.artist` before `user.username` for artist name
- now uses `publisher_metadata.release_title` before `title` for song title
- now uses `release_date` before `created_at` for album release year
- now uses `publisher_metadata.writer_composer` for song composer name

changelog:
- fixed a bug where the `Download` button did not appear on some tracks
- added SoundCloud track description to metadata (COMM id3 tag)
- improved DOM checks to know if a `Download` button should be added or not
- added `[scdl]` prefix to logs
- improved readme/documentation

changelog:
- fixed download button disappearing when playing a track in a set/playlist/album
- added support for `hls` transcoding format (which caused many tracks to not be downloaded)
- added support for private tracks downloading
- added `setInterval` clear when navigating away from the page
- improved overall code organization, structure & error handling
- improved id3 tagging
- improved URLs handling
- improved the way download buttons are added to the DOM
- improved the way button size is determined (now based on the parent group)
- improved the way some button group are ignored
- improved the way the track link is picked
- removed `logger()` function