Add routes for different parts of game

[ianjmacintosh]

Path	Role
/	Main menu
/play	Active game
/credits	Credits page
/instructions	Instructions screen

[ianjmacintosh]

I've made the routes, but moving components to get served from those routes instead of from a monolithic App page is a bigger ask.

Questions:

• What components match with each route? i.e., / is the main menu, which I think comes from a giant specially-styled Alert containing a Menu
• What props do those components currently inherit from App? Migrating them will be as big or small as that task is

I think making a separate task for building each route would improve my estimate accuracy and help me plan better