Create Security document for reporting private issues (#1021)

Adds security document for reporting private issues in terms of
Fabulously Optimized in general,
Resolves GitHub's community standards checklist which is currently 6 out
of 8.

---------

Co-authored-by: Madis Otenurm <[email protected]>

Author: Kichura

SECURITY.md

@@ -0,0 +1,10 @@
+# Security Policy
+
+## Reporting a Vulnerability
+
+If you discover a **security vulnerability**, please **do not** open a public issue. Instead, use one of the following **confidential contact methods**:
+
+* **GitHub:** Click the [Security tab](https://github.com/Fabulously-Optimized/fabulously-optimized/security), then [Report a vulnerability](https://github.com/Fabulously-Optimized/fabulously-optimized/security/advisories/new) and fill out the advisory details form.
+* **Discord:** Join our [Discord server](https://discord.gg/fabulously-optimized-859124104644788234) and visit the [#modmail](https://discord.com/channels/859124104644788234/1092684323515273247) channel for further instructions.
+
+If your issue is **not security-related** (e.g., bug reports, feature requests, or usage questions), please use the [Issues tab](https://github.com/Fabulously-Optimized/fabulously-optimized/issues) or use a relevant channel in the [Discord server](https://discord.gg/fabulously-optimized-859124104644788234).