docs(REAMDE): add Secman Core readme file about secman core

core/README.md

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+# Secman Core
+
+> **Secman Core** is the Backend Infrastructure for Secman products at [**api.secman.dev**](https://api.secman.dev).
+
+**SMCA** server was built with **GoLang**, **Rust**, **TypeScript**, **JavaScript**, **HCL**, **Terraform**, and **Docker**.
+
+## Security
+
+**1. Secman uses The Advanced Encryption Standard (AES) encryption algorithm with Galois/Counter Mode (GCM) symmetric-key cryptographic mode. Passwords encrypted with AES can only be decrypted with the passphrase defined in the _config.yml_ file.**
+
+**2. Endpoints are protected with security middlewares against attacks like XSS.**
+
+**3. Against SQL injection, Secman uses Gorm package to handle database queries which clears all queries.**