Add a proguard rule for XMLUtil

Co-authored-by: jobobby04 <[email protected]>

app/proguard-rules.pro

@@ -63,4 +63,7 @@
 -keepclassmembers class kotlinx.serialization.** {
     <methods>;
 }
-##---------------End: proguard configuration for kotlinx.serialization  ----------
+##---------------End: proguard configuration for kotlinx.serialization  ----------
+
+# XmlUtil
+-keep public enum nl.adaptivity.xmlutil.EventType { *; }