gg,examples: use a timer to limit the rate of updates in breakout, instead of a separate thread, restore ability to run in a browser through emscripten

examples/breakout/breakout.v

@@ -2,7 +2,6 @@ import gg
 import gx
 import math
 import rand
-import time
 import sokol.audio
 import os.asset
 import sokol.sgl
@@ -295,16 +294,12 @@ fn main() {
 		width:        g.width
 		height:       g.height
 		window_title: 'V Breakout'
-		sample_count: 2
-		init_fn:      fn (mut g Game) {
-			spawn fn (mut g Game) {
-				for {
-					g.update()
-					time.sleep(16666 * time.microsecond)
-				}
-			}(mut g)
-		}
 		frame_fn:     fn (mut g Game) {
+			dt := g.ctx.timer.elapsed().milliseconds()
+			if dt > 15 {
+				g.update()
+				g.ctx.timer.restart()
+			}
 			g.draw()
 		}
 		click_fn:     fn (x f32, y f32, btn gg.MouseButton, mut g Game) {

vlib/gg/gg.c.v

@@ -6,6 +6,7 @@ module gg
 import os
 import os.font
 import gx
+import time
 import sokol.sapp
 import sokol.sgl
 import sokol.gfx
@@ -202,6 +203,7 @@ pub mut:
 	font_inited bool
 	ui_mode     bool // do not redraw everything 60 times/second, but only when the user requests
 	frame       u64  // the current frame counted from the start of the application; always increasing
+	timer       time.StopWatch
 
 	mbtn_mask     u8
 	mouse_buttons MouseButtons // typed version of mbtn_mask; easier to use for user programs
@@ -285,6 +287,7 @@ fn gg_init_sokol_window(user_data voidptr) {
 	ctx.pipeline = &PipelineContainer{}
 	ctx.pipeline.init_pipeline()
 
+	ctx.timer = time.new_stopwatch()
 	if ctx.config.init_fn != unsafe { nil } {
 		$if android {
 			// NOTE on Android sokol can emit resize events *before* the init function is