chore: add SECURITY.md

Adapted from core sequelize repo
Fixes #1195

SECURITY.md

@@ -0,0 +1,16 @@
+# Security Policy
+
+## Supported versions
+
+The following table describes the versions of this project that are currently supported with security updates:
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 2.x     | :heavy_check_mark: |
+
+## Responsible disclosure policy
+
+At Sequelize, we prioritize security issues and will try to fix them as soon as they are disclosed.
+
+If you discover a security vulnerability, please create a security advisory [here](https://github.com/sequelize/sequelize-typescript/security/advisories/new).
+Otherwise, contact the project maintainers privately. You can find related information in [CONTACT.md](https://github.com/sequelize/sequelize/blob/main/CONTACT.md) of the core sequelize repository.