Incremental reviews (coderabbitai#181)

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### Summary by OpenAI

## Release Notes

Refactor: The `append` and `prepend` methods have been removed from the
`Commenter` class in `commenter.ts`, leaving only the `create` and
`replace` methods. The `mode` parameter has been updated to reflect this
change.

> "Out with the old, in with the new, 
> Commenter's got a fresh review. 
> Append and prepend are no more, 
> Create and replace are what's in store."
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