[llvm] [Github] Improve automatic new issue labelling (PR #65309)

[Vlad Serebrennikov via llvm-commits]

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Endilll wrote:

There are keywords to recognize backends (e.g. `AArch64`, `NVPTX`, `AMDGPU`) and LLVM components (e.g. `SelectionDAG`, `SelectionDAGISel`, `AsmParser`). I think they are worth listing here. 

https://github.com/llvm/llvm-project/pull/65309