Docs: add SECURITY.md, show security email address

Author: timmywil

SECURITY.md

@@ -0,0 +1,12 @@
+# Security Policy
+
+## Supported Versions
+
+The [latest released version](https://github.com/jquery/jquery/releases) of jQuery is supported.
+
+## Reporting a Vulnerability
+
+Please email security@jquery.com, and we will respond as quickly as possible.
+
+If the vulnerability is considered valid and accepted, a patch will be made for the latest jQuery version.
+If the vulnerability is deemed invalid, no further action is required.