Create SECURITY.md

SECURITY.md

+# Security Policy
+
+## Supported Versions
+
+Currently, we support security patches by committing changes and bumping the version published to PyPi.
+
+## Reporting a Vulnerability
+
+Found a vulnerability? Email us:
+- logan@llamaindex.ai
+- andrei@llamaindex.ai
+- simon@llamaindex.ai
+- jerry@llamaindex.ai