Register LLVM SPIR-V Backend as SPIR-V generator (#423)

* Register LLVM SPIR-V Backend as SPIR-V generator

* Change LLVM SPIR-V Backend vendor from "Intel" to "LLVM"
diff --git a/include/spirv/spir-v.xml b/include/spirv/spir-v.xml
index 7a837ec..80c1dec 100644
--- a/include/spirv/spir-v.xml
+++ b/include/spirv/spir-v.xml
@@ -93,7 +93,8 @@
         <id value="40"  vendor="NVIDIA" tool="Slang Compiler" comment="Contact Theresa Foley, tfoley@nvidia.com, https://github.com/shader-slang/slang/"/>
         <id value="41"  vendor="Zig Software Foundation" tool="Zig Compiler" comment="Contact Robin Voetter, https://github.com/Snektron"/>
         <id value="42"  vendor="Rendong Liang" tool="spq" comment="Contact Rendong Liang, admin@penguinliong.moe, https://github.com/PENGUINLIONG/spq-rs"/>
-        <unused start="43" end="0xFFFF" comment="Tool ID range reservable for future use by vendors"/>
+        <id value="43"  vendor="LLVM" tool="LLVM SPIR-V Backend" comment="Contact Michal Paszkowski, michal.paszkowski@intel.com, https://github.com/llvm/llvm-project/tree/main/llvm/lib/Target/SPIRV"/>
+        <unused start="44" end="0xFFFF" comment="Tool ID range reservable for future use by vendors"/>
     </ids>
 
     <!-- SECTION: SPIR-V Opcodes and Enumerants -->