[Doc] Add sphinx build for vllm-ascend (#55)

### What this PR does / why we need it?

This patch enables the doc build for vllm-ascend

- Add sphinx build for vllm-ascend
- Enable readthedocs for vllm-ascend
- Fix CI:
- exclude vllm-empty/tests/mistral_tool_use to skip `You need to agree
to share your contact information to access this model` which introduce
in
314cfade02
- Install test req to fix
https://github.com/vllm-project/vllm-ascend/actions/runs/13304112758/job/37151690770:
      ```
      vllm-empty/tests/mistral_tool_use/conftest.py:4: in <module>
          import pytest_asyncio
      E   ModuleNotFoundError: No module named 'pytest_asyncio'
      ```
  - exclude docs PR

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
1. test locally:
    ```bash
    # Install dependencies.
    pip install -r requirements-docs.txt
    
    # Build the docs and preview
    make clean; make html; python -m http.server -d build/html/
    ```
    
    Launch browser and open http://localhost:8000/.

2. CI passed with preview:
    https://vllm-ascend--55.org.readthedocs.build/en/55/

Signed-off-by: Yikun Jiang <yikunkero@gmail.com>

docs/source/installation.md

@@ -0,0 +1,55 @@
+# Installation
+
+## Dependencies
+| Requirement  | Supported version | Recommended version | Note |
+| ------------ | ------- | ----------- | ----------- | 
+| Python | >= 3.9 | [3.10](https://www.python.org/downloads/) | Required for vllm |
+| CANN         | >= 8.0.RC2 | [8.0.RC3](https://www.hiascend.com/developer/download/community/result?module=cann&cann=8.0.0.beta1) | Required for vllm-ascend and torch-npu |
+| torch-npu    | >= 2.4.0   | [2.5.1rc1](https://gitee.com/ascend/pytorch/releases/tag/v6.0.0.alpha001-pytorch2.5.1)    | Required for vllm-ascend |
+| torch        | >= 2.4.0   | [2.5.1](https://github.com/pytorch/pytorch/releases/tag/v2.5.1)      | Required for torch-npu and vllm required |
+
+## Prepare Ascend NPU environment
+
+Below is a quick note to install recommended version software:
+
+### Containerized installation
+
+You can use the [container image](https://hub.docker.com/r/ascendai/cann) directly with one line command:
+
+```bash
+docker run \
+    --name vllm-ascend-env \
+    --device /dev/davinci1 \
+    --device /dev/davinci_manager \
+    --device /dev/devmm_svm \
+    --device /dev/hisi_hdc \
+    -v /usr/local/dcmi:/usr/local/dcmi \
+    -v /usr/local/bin/npu-smi:/usr/local/bin/npu-smi \
+    -v /usr/local/Ascend/driver/lib64/:/usr/local/Ascend/driver/lib64/ \
+    -v /usr/local/Ascend/driver/version.info:/usr/local/Ascend/driver/version.info \
+    -v /etc/ascend_install.info:/etc/ascend_install.info \
+    -it quay.io/ascend/cann:8.0.rc3.beta1-910b-ubuntu22.04-py3.10 bash
+```
+
+You do not need to install `torch` and `torch_npu` manually, they will be automatically installed as `vllm-ascend` dependencies.
+
+### Manual installation
+
+Or follow the instructions provided in the [Ascend Installation Guide](https://ascend.github.io/docs/sources/ascend/quick_install.html) to set up the environment.
+
+## Building
+
+### Build Python package from source
+
+```bash
+git clone https://github.com/vllm-project/vllm-ascend.git
+cd vllm-ascend
+pip install -e .
+```
+
+### Build container image from source
+```bash
+git clone https://github.com/vllm-project/vllm-ascend.git
+cd vllm-ascend
+docker build -t vllm-ascend-dev-image -f ./Dockerfile .
+```