Make the viewport (and hud and all) 100% width 100% height

[gyril]

The viewport size should dictate the size of the camera.

We must use JS to detect the width and height of the player's window, then feed it to the viewport + camera.

[gyril]

Mostly done.

Now we should also:

• handle resize
• have a bigger map because now it looks weird to see the void so much when in zoom 1

[gyril]

we'll come back to the resize thing when it's a problem