docs(github): add security policy (#885)

Author: cotes2020

.github/SECURITY.md

@@ -0,0 +1,12 @@
+# Security Policy
+
+## Supported Versions
+
+| Version | Supported          |
+|---------| ------------------ |
+| 5.x     | :white_check_mark: |
+| < 5.0.0 | :x:                |
+
+## Reporting a Vulnerability
+
+If you find a vulnerability, please report it to `cotes.chung@gmail.com`. We will try our best to respond within a week. Thank you for your time!