Update CODEOWNERS (#11785)

### Summary
[PLEASE REMOVE] See [CONTRIBUTING.md's Pull
Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests)
for ExecuTorch PR guidelines.

[PLEASE REMOVE] If this PR closes an issue, please add a `Fixes
#<issue-id>` line.

[PLEASE REMOVE] If this PR introduces a fix or feature that should be
the upcoming release notes, please add a "Release notes: <area>" label.
For a list of available release notes labels, check out
[CONTRIBUTING.md's Pull
Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests).

### Test plan
[PLEASE REMOVE] How did you test this PR? Please write down any manual
commands you used and note down tests that you have written if
applicable.

Author: mergennachin

CODEOWNERS

@@ -48,7 +48,7 @@
 /extension/flat_tensor @lucylq
 /extension/gguf_util @larryliu0820
 /extension/kernel_util @kimishpatel @manuelcandales @swolchok
-/extension/llm @jackzhxng @larryliu0820 @swolchok
+/extension/llm @jackzhxng @larryliu0820 @swolchok @mergennachin
 /extension/memory_allocator @JacobSzwejbka @swolchok
 /extension/module @shoumikhin
 /extension/parallel @kimishpatel @swolchok