[GitHub] Add codeowners for mlir/spirv (#72412)

Add @antiagainst and @kuhar as codeowners for SPIR-V in MLIR. This is to
assign reviewers automatically.

We already have a self-serve mechanism for subscribing to mlir/spirv
issues (@llvm/pr-subscribers-mlir-spirv), but this codeowners change
reflects a narrower set of core authors/maintainers for this part of the
mlir.

Author: kuhar

.github/CODEOWNERS

@@ -32,3 +32,18 @@
 /clang/www/make_cxx_dr_status @Endilll
 
 /lldb/ @JDevlieghere
+
+# SPIR-V in MLIR.
+/mlir/include/mlir/Dialect/SPIRV/ @antiagainst @kuhar
+/mlir/include/mlir/Target/SPIRV/ @antiagainst @kuhar
+/mlir/include/mlir/Conversion/SPIRVTo*/ @antiagainst @kuhar
+/mlir/include/mlir/Conversion/*ToSPIRV/ @antiagainst @kuhar
+/mlir/lib/Dialect/SPIRV/ @antiagainst @kuhar
+/mlir/lib/Target/SPIRV/ @antiagainst @kuhar
+/mlir/lib/Conversion/SPIRVTo*/ @antiagainst @kuhar
+/mlir/lib/Conversion/*ToSPIRV/ @antiagainst @kuhar
+/mlir/test/Dialect/SPIRV/ @antiagainst @kuhar
+/mlir/test/Target/SPIRV/ @antiagainst @kuhar
+/mlir/test/lib/Dialect/SPIRV/ @antiagainst @kuhar
+/mlir/unittests/Dialect/SPIRV/ @antiagainst @kuhar
+/mlir/tools/mlir-tblgen/SPIRVUtilsGen.cpp @antiagainst @kuhar