Allow players to join an existing game

[kingdomlevel]

Any user who is not the host:

• should be able to enter a valid game URL and be directed to a Room in lobby state
• should not be able to see game admin panel

! Depends on #11

[kingdomlevel]

As part of this issue we should also visualise a list of players in the lobby! maybe a new component PlayerList in lobby (or in room so we can re-use in game...?)

[kingdomlevel]

This will require:

• linking up the join game button to push /gameCode to history
• making a new component PlayerList to show the nicknames in current room

Also should this not include a limitation on players? If I am the host and set it to 6 players, and my amigos amigo tries to join they should get a message saying "Lobby is full."?

[kingdomlevel]

Also should this not include a limitation on players? If I am the host and set it to 6 players, and my amigos amigo tries to join they should get a message saying "Lobby is full."?

I would say this would depend on the admin panel issue #12 - i'm tempted to say that the limit could be incorporated into #12 or be its own issue after?