Personalized data on main page

[ConcernedHobbit]

Add some client-side JS to have some record keeping in localStorage

localStorage.hits: {
  [slug]: {
    lastVisited: number<timestamp>;
    timesVisited: number; 
  }
}
localStorage.favorites: {
  [slug]: number<timestamp>;
}
localStorage.hidden: {
  [slug]: number<timestamp>;
}

• Show favorites on main page
• Allow organizing songs by times visited OR alphabetically
• Hide hidden songs from main page (can be 'show hidden' button at end); if visiting a hidden page, show warning first ("are you sure you want to view?")