switched the foreground observation for the more reliable didBecomeAc…

[morgz]

In my testing I've found the foreground observation doesn't work when you:

• Use App Switcher
• Swipe from top right or top left for control centre / notifications.

See this forum post for more detail. I've switched to UIApplication.didBecomeActiveNotification which I found much more reliable.

[dsrees]

Thanks 👍🏼