Callback whether is image is getting loaded from the network or cache.

## 🚀 Feature Requests

Right now , there is no callback to know whether image that is getting loaded is coming from network or the cache database.
I think it would be quite great , if we can somehow get the callback regarding the same.

CacheNetworkImage(
source:(source){}
),

### Platforms affected (mark all that apply)
- [ ] :iphone: iOS
- [ ] :robot: Android