F-InApp Demo

1: Multiple subscriptions.
2: One-time purchase (Non-Consumable purchase).
3: Unlimited purchases (Consumable purchases).
5: Remove Ads purchase (Admob and Facebook)
6: Restore owned purchase button.
7: Auto subscription check and activate
8: [New] Subscription Upgrade and Downgrade
9: [New] Store and read coins and subscriptions from Firebase