add "ticks per render" metric

src/client/InputHandler.ts

@@ -131,6 +131,8 @@ export class TickMetricsEvent implements GameEvent {
     public readonly tickDelay?: number,
     // Number of turns the client is behind the server (if known)
     public readonly backlogTurns?: number,
+    // Number of ticks applied since last render
+    public readonly ticksPerRender?: number,
   ) {}
 }