[Doc] Refactor and init user story page (#1224)

### What this PR does / why we need it?
This PR refactor the user stories page:
- Move it to community
- Add initial info of LLaMA-Factory, Huggingface/trl, MindIE Turbo,
GPUStack, verl
- Add a new page for LLaMA-Factory

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

### How was this patch tested?
Preview locally

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

docs/source/index.md

@@ -66,11 +66,5 @@ developer_guide/evaluation/index
 :maxdepth: 1
 community/governance
 community/contributors
-:::
-
-% User stories about vLLM Ascend project
-:::{toctree}
-:caption: User Story
-:maxdepth: 1
-user_stories/index
+community/user_stories/index
 :::