Added chokidar to watch for folder changes; added folder-watcher;
passing state to delayedInit on main; added default values for new
preferences; added “Auto add torrents” preference with its checkbox and
path selector; TODO: start/stop watching on preference change, start
watching on init, add dialog when trying to enable preference without a
torrents folder.
Before, the gradient transparent black overlay made text hard to read in some cases. Torrents without a poster image showed up in blue-gray and didn't look good.
