Post-jam feature update

There were quite a lot of items left on the todo list at the moment I've submitted the final version of the game to the jam, so I've decided to complete those and make the game a little more polished and a little less rough around the edges. Unless there's popular demand, that's probably the last "feature update" for the game, but that's okay, I'm quite happy with it now.

What's new:

• Background music by the amazing Alexandr Zhelanov - check out his YouTube  and SoundCloud, he's amazing!
• Basic sound effects for snapping chains and chains landing in lanes.
• Some more visual effects ("dust" particles).
• Input is now more responsive since it's handled by the Mouse object instead of the Touch object, clicking/tapping fast moving links is now easier.
• PlayFab requires at least 3 characters for display names, so I've added a basic string length check for the leaderboard submission.
• Minor changes to wording here and there.