Backport "Add the link to scala's security policy" to 3.5.2 (#21452)

Backports #21220 to the 3.5.2 branch.

PR submitted by the release tooling.
[skip ci]

SECURITY.md

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+# Security Policy
+
+The details about the security policy of the Scala Programming Language organisation can be found in [https://scala-lang.org/security](https://scala-lang.org/security).
+
+For any additional information related to our security policy, please contact [[email protected]](mailto:[email protected]).