Maybe fix Firebase crashes

See https://github.com/firebase/firebase-android-sdk/issues/3507

app/proguard-rules.pro

@@ -69,4 +69,8 @@
 ##---------------End: proguard configuration for kotlinx.serialization  ----------
 
 # XmlUtil
--keep public enum nl.adaptivity.xmlutil.EventType { *; }
+-keep public enum nl.adaptivity.xmlutil.EventType { *; }
+
+# Firebase
+-keep class com.google.firebase.installations.** { *; }
+-keep interface com.google.firebase.installations.** { *; }