make movement speed configurable.

js/pixl/public/trixl.html

		trixl.start();
		trixl.speed = { move: 0.1, turn: 0.01 }
		trixl.input = {};
		trixl.input.keys = new Set();
		document.addEventListener("keydown", function(ev) {
			}
			if (isPressed(37) || isPressed(65)) { // left || a
				trixl.camera.sideways(-0.1);
				trixl.camera.sideways(-trixl.speed.move);
			}
			if (isPressed(38) || isPressed(87)) { // up || w
				trixl.camera.forward(-0.1);
				trixl.camera.forward(-trixl.speed.move);
			}
			if (isPressed(39) || isPressed(68)) { // right || d
				trixl.camera.sideways(0.1);
				trixl.camera.sideways(trixl.speed.move);
			}
			if (isPressed(40) || isPressed(83)) { // down || s
				trixl.camera.forward(0.1);
				trixl.camera.forward(trixl.speed.move);
			}
		});
			}
			var diff = { x: mouse.last.x - ev.clientX, y: mouse.last.y - ev.clientY };
			trixl.camera.rotate(diff.x * 0.01, diff.y * 0.01);
			trixl.camera.rotate(diff.x * trixl.speed.turn, diff.y * trixl.speed.turn);
			mouse.last = {x: ev.clientX, y: ev.clientY};
		});