Multiplayer

[manuq]

Notes:

• This is only to handle multiple Player components and 2 players controls, like in Moddable Pong. The camera changes will be addressed separately in #9
• The game logic didn't change. So it's a "coop": all players share the same lives and score for coins, and when one dies all of them respawn. In the future we could add other modes.

https://github.com/endlessm/moddable-platformer/issues/8

[manuq]

Thanks @dylanmccall . Ready for review again!

• Players are now renamed to Player 1 / Player 2 (not "left / right" like in Moddable Pong)
• Player controls are now all custom (not reusing the UI builtin actions) and should support joysticks too (untested)
• Also I found that the falling platforms were hardcoding the player name, so it didn't work for multiple players. Fixed.

I realize that it may be confusing to have a Player property in a Player scene instance. The scene came first, but it really should be renamed to "PlayerCharacter", "Avatar" or something.

If this gets merged, I will do the same thing in Moddable Pong.