added route for deck view & adding cards

[janethuangg]

this PR just adds a couple of routes so that we can align on what routes display what

• pokedek.com/deck/ will be the page that people can view the deck and add cards from
• pokedek.com/deck//add will be the page where people can add cards to the deck with id

there's no way to get to the links via web interaction yet so you can just directly type in the link e.g. http://localhost:3000/deck/123