[Security Center] Update changelog (#16981)

* [Security Center] Update changelog

* Update src/content/changelogs/security-center.yaml

Co-authored-by: angelampcosta <[email protected]>

---------

Co-authored-by: angelampcosta <[email protected]>

Author: Maddy-Cloudflare

src/content/changelogs/security-center.yaml

@@ -8,3 +8,7 @@ entries:
   - publish_date: "2024-07-22"
     description: |-
       - Customers can now archive multiple Security Insights at the same time. Go to **Security Center** > **Security Insights** and select the insights to archive.
+
+  - publish_date: "2024-09-19"
+    description: |-
+      - Customers can now create a `security.txt` file file to provide the security research team with a standardized way to report vulnerabilities.