[feature request] enable repeat track by default

provide an option in sc-repeat-playlist extension settings to enable "repeat track" feature by default

so that when a random soundcloud track page is opened, "repeat track" button is already enabled

Start by locating the extension settings and the repeat-track behavior used when a SoundCloud track page opens. Add a setting that controls the default state of the "repeat track" button, and verify that enabling it makes the button active on newly opened random track pages.

Written by the indexing model from the issue text.