Included multi-node DeepSeekv3 example

[roG0d]

Motivation

Include an actual DeepSeek v3 multinode example and a testing workload in 2 nodes with 8xH200 GPUs each.

Modifications

Included markdown for the sglang/benchmark/README.md

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[roG0d]

Tagging #2450