R8 Proguard mappings are not propagated to the resource shrinker

[mauriciogg]

Currently there is no way to pass proguard mappings to the resource shrinker. Without it a bunch of resource that should that should be kept are removed instead. This is currently not supported directly by the shrinker tool. I've filed a feature request on android requesting support, but if the feature is not accepted we will need to implement our own wrapper.

[mauriciogg]

I've added a implementation for the resource shrinker cli that accepts proguard mappings here #149. At least in our builds it does not really seems to have any effect though. Additional resources that were being stripped in our builds due to the use of precise shinking option not because of the missing proguard mapping, so im not really sure this is entirely necessary