Add to navbar link to SafetyNet readme.

Change-Id: I50eb3b4e94b72efe5978b02db137fab3eb6b21da
Reviewed-on: https://pdfium-review.googlesource.com/11090
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/navbar.md b/navbar.md
index a7f9307..c12cf11 100644
--- a/navbar.md
+++ b/navbar.md
@@ -9,5 +9,6 @@
 * [Home](/README.md)
 * [Getting Started](/docs/getting-started.md)
 * [V8 Getting Started](/docs/v8-getting-started.md)
+* [SafetyNet](/docs/safetynet.md)
 
 [home]: /README.md