Merge pull request #2566 from SatoshiPortal/feat/security-md

add SECURITY.md file with new email

Author: basantagoswami

SECURITY.md

@@ -0,0 +1,9 @@
+# Security Policy
+
+## Reporting a Vulnerability
+
+Please report security vulnerabilities privately to **security@bullbitcoin.com**.
+
+Do not open a public issue for security reports.
+
+Include as much detail as possible (affected version, steps to reproduce, impact). We will acknowledge your report and keep you updated on the fix.