Add API toi check both composition and network cache

Hey there,

Is your feature request related to a problem? Please describe. My team has implemented feature with resource storing on CDN. And to provide a convimnient API we need to check Lottie Cache (both composition and network) whether the animation json has been already cached or not. Fow now, we use workarounds to achive that.

Describe the solution you'd like Public method isCached(url: String) in NetworkCache Or another public method that provide isCached from both LruCache and DiskCache

Describe alternatives you've considered The only way to get "isCached" fro now is to do that: L.networkCache(context).fetch(url) != null or call networkFetcher::fetchFromCache using reflection or some other workarounds.

Additional context Add any other context or screenshots about the feature request here.