Add support for flagging xml and png files

This extends the previous change that added the ability to flag resource
directories so that xml and png files are now supported.

Test: Automated
Bug: 329436914
Flag: EXEMPT Aconfig not supported on host tools
Change-Id: I9f2b6b15ba0078ea33188f1a554377784cff9786
diff --git a/tools/aapt2/Resource.h b/tools/aapt2/Resource.h
index 446fdd4..0d261ab 100644
--- a/tools/aapt2/Resource.h
+++ b/tools/aapt2/Resource.h
@@ -243,6 +243,12 @@
 
   // Exported symbols
   std::vector<SourcedResourceName> exported_symbols;
+
+  // Flag status
+  FlagStatus flag_status = FlagStatus::NoFlag;
+
+  // Flag
+  std::optional<FeatureFlagAttribute> flag;
 };
 
 /**