Enhance MonitorPageNetwork function

[hawarir]

I just realised from the doc, ListenTarget runs its function synchronously:
"Note that the function is called synchronously when handling events. The function should avoid blocking at all costs. For example, any Actions must be run via a separate goroutine."

https://godoc.org/github.com/chromedp/chromedp#ListenTarget

We'll need to takeout the writer from inside the function and preferably using goroutine to run the function logic.