Add a CPEPrefix for libtiff.

Help automated system generate notifications for known vulnerabilities.

Change-Id: I368e42f536e96d6b32a31923b62314c34bff732c
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/91354
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/third_party/libtiff/README.pdfium b/third_party/libtiff/README.pdfium
index bcde8e9..269484b 100644
--- a/third_party/libtiff/README.pdfium
+++ b/third_party/libtiff/README.pdfium
@@ -1,6 +1,7 @@
 Name: LibTIFF
 URL: http://www.simplesystems.org/libtiff/
 Version: 4.2.0
+CPEPrefix: cpe:/a:libtiff:libtiff:4.2.0
 Security Critical: yes
 License: BSD