Rework state management

Install redux-toolkit (instructions - https://redux-toolkit.js.org/introduction/getting-started#an-existing-app)
Convert game logic to serializable plain object, instead of class
Root state has one piece - game state
Actions: makeMove (takes cell number), startNewGame (no parameters)
Rip out prop-drilling; Cell can dispatch makeMove, NewGameButton can dispatch startNewGame.

DylanSp / tic-tac-toe-react