Add proguard rules for using Gson TypeToken

Author: esensar

app/proguard-rules.pro

@@ -25,3 +25,9 @@
     public static <1> INSTANCE;
     kotlinx.serialization.KSerializer serializer(...);
 }
+
+# Needed for using TypeToken with Gson
+# Taken from: https://r8.googlesource.com/r8/+/refs/heads/main/compatibility-faq.md#troubleshooting-gson-gson
+-keepattributes Signature
+-keep class com.google.gson.reflect.TypeToken { *; }
+-keep class * extends com.google.gson.reflect.TypeToken