minimal functionality

• allow user to move/capture pieces with click and drag
• when user moves a piece, send the move to the engine
  • call a wasm function that returns a random legal move -- we havent implemented the search yet
• update the board state with the engine output
• support promotion

stretch goal

• check if a move is valid
• prevent player from moving black pieces
• disallow player to move twice in a row (before engine has a chance to move)
• eval bar (display the engine's evaluation of the position)
• determines when someone wins/draws/loses? (maybe for engine)
• make promotion piece selector look pretty + pop up when user attempts to promote