Add examples for returning hidden states when using the server

[Qiaolin-Yu]

Motivation

Add more examples for returning hidden states.

Modifications

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
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• Please feel free to join our Slack channel at https://slack.sglang.ai to discuss your PR.

[zhaochenyang20]

Add how to launch server in the examples. Refer to our docs.

[Qiaolin-Yu]

Add how to launch server in the examples. Refer to our docs.

done