feat: Add `append` and `last_chunk` to `add_artifact` method on `TaskUpdater` #186

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@coolbeevip

The following contributors were found for this pull request:

✅ a49f2a5 Author: @coolbeevip <zh****ei@apache.org>
✅ d211772 Co-Author: @holtskinner <13262395+holtskinner@users.noreply.github.com>
✅ 344cab0 Author: @kthota-g <kc****a@google.com>

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