Add proguard rule that allows to further optimize custom views
`View.isInEditMode()` will always be `false` when the app is run on the device.
-dontnote com.fsck.k9.ui.messageview.**
-dontnote com.fsck.k9.view.**
+-assumevalues class * extends android.view.View {
+ boolean isInEditMode() return false;
+}
+
-keep public class org.openintents.openpgp.**
-keepclassmembers class * extends androidx.appcompat.widget.SearchView {
