Add Patchstack security vulnerability disclosure program link to faq

omnisend-for-gravity-forms/readme.txt

@@ -46,6 +46,9 @@ Every Omnisend customer gets our award-winning support, 24/7—even on the free
 = Where can I find Omnisend Terms? =
 Read Omnisend [Terms of Use](https://www.omnisend.com/terms)
 
+= How can I report security bugs?
+You can report security bugs through the Patchstack Vulnerability Disclosure Program. The Patchstack team help validate, triage and handle any security vulnerabilities. [Report a security vulnerability.](https://patchstack.com/database/vdp/omnisend-for-gravity-forms-add-on)
+
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