Add proguard rules for Android

[chris-fitzgerald-ck]

Is your feature request related to a problem? Please describe.
Integrating player into a library with minification on would be easier with a sample proguard file. Defining the least needed rules would also allow clients to integrate while adding the most obfuscated and minified build possible.

Describe the solution you'd like
It would be nice to have a sample proguard file that keeps all the classes that are used across the bridge with reflection, but still allows unused code to be stripped (or at least obfuscated).

Additional context
Currently, our rules look like this for player:

# These libraries use reflection for bridge methods between the JNI and JVM
-keep @com.facebook.jni.annotations.DoNotStrip public class * { *; }
-keep @com.facebook.jni.annotations.DoNotStripAny public class * { *; }
-keep class com.intuit.playerui.** { *; }
-keepnames class * extends com.intuit.playerui.jsi.HostFunctionInterface { *; }