[llvm] docs: Add an incident response guide (PR #133567)

[Vlad Serebrennikov via llvm-commits]

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@@ -0,0 +1,87 @@
+============================
+LLVM Incident Response Guide
+============================
+
+Purpose
+=======
+
+The purpose of this document is to outline how a project administrator should respond to
+malicious or unwanted content that appears on LLVM infrastructure.  This includes but
+is not limited to: malicious code checked into the GitHub repository,  unauthorized access
+to LLVM controlled servers, or compromise of community owned resources like buildbots
----------------
Endilll wrote:

```suggestion
to LLVM controlled servers, or compromise of community-owned resources like buildbots
```

https://github.com/llvm/llvm-project/pull/133567