Training: Add Fine-Tune API Docs

Signed-off-by: Andrey Velichkevich <[email protected]>

content/en/docs/components/training/user-guides/_index.md

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+title = "User Guides"
+description = "User guides for Kubeflow Training Operator"
+weight = 20
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content/en/docs/components/training/user-guides/fine-tuning.md

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+title = "Fine-Tuning API for LLMs"
+description = "How to fine-tune LLMs with Training Operator"
+weight = 10
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+
+{{% alert title="Warning" color="warning" %}}
+This feature is in **alpha** stage and Kubeflow community is looking for your feedback. Please
+share your experience using #kubeflow-training-operator Slack channel or
+[Kubeflow Training Operator GitHib](https://github.com/kubeflow/training-operator/issues/new).
+{{% /alert %}}
+
+## Architecture
+
+<img src="/docs/components/training/images/fine-tune-llm-api.drawio.svg"
+  alt="Fine-Tune API for LLMs"
+  class="mt-3 mb-3">