[llvm] [SPIR-V] Extend SPIRVUsage.rst document (PR #84744)

[Michal Paszkowski via llvm-commits]

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@@ -62,24 +67,90 @@ to specify the target triple:
      OS                    Description
      ===================== ============================================================
      *<empty>*/``unknown``  Defaults to the OpenCL runtime.
+     ``vulkan``             Vulkan shader runtime.
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michalpaszkowski wrote:

Yep, this is a good idea! Will work on this and update the patch.

https://github.com/llvm/llvm-project/pull/84744