added badges + github templates

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+Only the latest release of `proton-sdk-rs` receives security updates. If you discover a vulnerability, please update to the latest version before reporting.
+
+| Version | Supported |
+| ------- | --------- |
+| >= 0.1.x | :white_check_mark: |
+| < 0.1.0 | :x: |
+
+## Reporting a Vulnerability
+
+We take the security of this project seriously. Because this SDK handles highly sensitive account credentials, session tokens, and zero-knowledge cryptographic keys, we request that security vulnerabilities be reported responsibly.
+
+**Please do not open a public GitHub issue for security-related bugs.**
+
+To report a vulnerability:
+1. Send an email to the project maintainer at `contact@narl.io` (referencing the email in `Cargo.toml`).
+2. Provide a detailed description of the vulnerability, including steps to reproduce, code snippets, or a proof of concept if available.
+3. We will acknowledge receipt of your report within 48 hours and work with you to coordinate a security release.
+
+Thank you for helping keep this SDK secure!