[Doc] Add versioning_policy doc (#62)

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

This patch add the versioning policy doc for vllm-ascend

Reference:
- https://spark.apache.org/versioning-policy.html
- https://docs.openstack.org/project-team-guide/stable-branches.html
- https://github.com/pytorch/pytorch/blob/main/RELEASE.md

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

### How was this patch tested?
preview: https://vllm-ascend--62.org.readthedocs.build/en/62/

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

docs/source/conf.py

@@ -78,7 +78,7 @@ exclude_patterns = [
     '.venv',
     'README.md',
     # TODO(yikun): Remove this after zh supported
-    'developer_guide/contributing.zh.md'
+    '**/*.zh.md'
 ]
 
 # -- Options for HTML output -------------------------------------------------