[ci] chore: add codeowner

[tardis-key]

What does this PR do?

add codeowner in npu folder
/recipe/dapo and /examples/grpo_trainer: model scripts of npu
/verl/models/transformers: npu_patch for transformers

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[gemini-code-assist]

Code Review

This pull request adds @tardis-key as a code owner for /recipe/dapo, /examples/grpo_trainer, and /verl/models/transformers. The changes are straightforward. However, I've identified a potential maintainability issue: the new paths for /examples/grpo_trainer and /verl/models/transformers are assigned a single code owner. This creates a single point of failure and can lead to review bottlenecks. I've left comments suggesting adding at least one more owner to these paths to mitigate this risk.