More Proguard fixes for extensions

app/proguard-rules.pro

@@ -2,8 +2,10 @@
 
 # Keep extension's common dependencies
 -keep,allowoptimization class eu.kanade.tachiyomi.** { public protected *; }
+-keep,allowoptimization class androidx.preference.** { *; }
 -keep,allowoptimization class kotlin.** { public protected *; }
 -keep,allowoptimization class okhttp3.** { public protected *; }
+-keep,allowoptimization class okio.** { public protected *; }
 -keep,allowoptimization class rx.** { public protected *; }
 -keep,allowoptimization class org.jsoup.** { public protected *; }
 -keep,allowoptimization class com.google.gson.** { public protected *; }