Add updated cpe for vulnerability scanners

Bug: b/201572953
Change-Id: I3beae07f5b81e9aaf2ca7fe3f157e7c9b4ec10e1
diff --git a/METADATA b/METADATA
index 812f45a..7288841 100644
--- a/METADATA
+++ b/METADATA
@@ -12,4 +12,7 @@
     month: 6
     day: 10
   }
+  security {
+      tag: "NVD-CPE2.3:cpe:/a:libpng:libpng:1.6.37"
+  }
 }