Adding timer for creating time controlled variants in the game.

[ashishpapanai]

With the evolution of chess different variants have come up and are recognised by FIDE. ChessJS is expected to add these time control with the help of contributors.

Needed time controls:

• Classical: No time control or 30 minutes with 20-second increment after each move for either side.
• Rapid: 15 mins with 10 seconds increment after each move for either side.
• Blitz: 5 mins with 10 seconds increment after each move for either side.
• Bullet: 2 mins with 10 seconds increment after each move for either side.

The game will end after the timer of any side runs out and the side with time left on the clock will be declared as the winner.

The timer needs to be displayed to both the user at the top right corner of the board for black and bottom right for the white pieces.