Add link to URL display guidelines.

Change-Id: I017e3d07568b22b39ee322e4d0a41729ce8b8217
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4519121
Reviewed-by: Emily Stark <[email protected]>
Commit-Queue: Emily Stark <[email protected]>
Auto-Submit: Adrian Taylor <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1142148}
diff --git a/docs/security/rules.md b/docs/security/rules.md
index 4022e920..050f1f1 100644
--- a/docs/security/rules.md
+++ b/docs/security/rules.md
@@ -14,6 +14,7 @@
 * [Controlling access to powerful web platform
   features](permissions-for-powerful-web-platform-features.md)
 * [Security considerations for browser UI](security-considerations-for-browser-ui.md)
+* [Guidelines for URL display](url_display_guidelines/url_display_guidelines.md)
 
 You can also find our position on various matters in the [security FAQ](faq.md):
 for example, on local attackers or on the privilege accorded to enterprise