Add vLLM Ascend project governance docs (#1070)

### What this PR does / why we need it?
Add vLLM Ascend project governance and first contributors docs

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

### How was this patch tested?
Preview

Closes: https://github.com/vllm-project/vllm-ascend/issues/828
Closes: https://github.com/vllm-project/vllm-ascend/issues/929

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

docs/source/index.md

@@ -58,6 +58,14 @@ developer_guide/versioning_policy
 developer_guide/evaluation/index
 :::
 
+% How to involve vLLM Ascend
+:::{toctree}
+:caption: Community
+:maxdepth: 1
+community/governance
+community/contributors
+:::
+
 % User stories about vLLM Ascend project
 :::{toctree}
 :caption: User Story