sim: implement time.ticks_add

sim/fakes/time.py

@@ -8,4 +8,7 @@ def ticks_ms():
     return int(_time.time() * 1000)
 
 def ticks_diff(a, b):
-    return a - b
\ No newline at end of file
+    return a - b
+
+def ticks_add(a, b):
+    return a + b