start/stop using the space bar.

js/pixl/public/trixl.html

@@ -300,6 +300,16 @@
		}
		trixl.start();
		document.addEventListener("keydown", function(ev) {
			if (ev.keyCode == 32) {
				if (trixl.step.reqId == null) {
					trixl.start();
				} else {
					trixl.stop();
				}
			}
		});
	</script>
</body>
</html>