chore: Security policy thingy

SECURITY.md

+# Security Policy
+
+## Supported Versions
+
+Only releases of the latest major-minor-release-line are supported.
+
+For example, if the latest major-release-line is 4.1.x, then the following matrix would apply: 
+
+| Version | Supported          |
+|---------|--------------------|
+| 4.1.x   | :white_check_mark: |
+| 4.0.x   | :x:                |
+| < 4.0   | :x:                |
+| 3.x.x   | :x:                |
+| 2.x.x   | :x:                |
+| 1.x.x   | :x:                |
+
+Similarly, if the latest major-minor-release-line is 5.3.x, then the following matrix would apply:
+
+| Version | Supported          |
+|---------|--------------------|
+| 5.3.x   | :white_check_mark: |
+| 5.0.x   | :x:                |
+| < 5.0   | :x:                |
+| 4.x.x   | :x:                |
+| 3.x.x   | :x:                |
+| 2.x.x   | :x:                |
+| 1.x.x   | :x:                |
+
+If a newer major-minor-line is released, keeping with the examples above, i.e. 4.2.x or 5.4.x, then the matrices above
+should help you to determine which versions will receive security-updates.
+
+## Reporting a Vulnerability
+
+Vulnerabilities should always be reported on GitHub, at https://github.com/Griefed/ServerPackCreator/issues
\ No newline at end of file