Add Qwen3-Next Tutorial

[ming1212]

What this PR does / why we need it?

Does this PR introduce any user-facing change?

How was this patch tested?

• vLLM version: v0.11.2
• vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.2

[gemini-code-assist]

Code Review

This pull request introduces a new tutorial for using the Qwen3-Next model. The documentation is comprehensive and provides clear steps for users. My review focuses on ensuring consistency within the provided commands. I've identified a minor inconsistency in the model name used in one of the commands and suggested a correction to improve clarity and prevent potential user errors.

[gemini-code-assist]

The model name vllm-ascend/Qwen3-Next-80B-A3B-Instruct in this command is inconsistent with the model name used elsewhere in this tutorial (Qwen/Qwen3-Next-80B-A3B-Instruct). For consistency and to prevent user errors, please use the same model name throughout the guide.

Suggested change

	vllm bench serve --model vllm-ascend/Qwen3-Next-80B-A3B-Instruct --dataset-name random --random-input 200 --num-prompt 200 --request-rate 1 --save-result --result-dir ./
	vllm bench serve --model Qwen/Qwen3-Next-80B-A3B-Instruct --dataset-name random --random-input 200 --num-prompt 200 --request-rate 1 --save-result --result-dir ./

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