### What this PR does / why we need it?
To help more developers quickly get started with vLLM, we need to write
clear and easy-to-understand code documentation and technical
interpretations. This will effectively lower the learning curve, attract
more excellent contributors, and collectively build a better developer
community.
Add ModelRunner_prepare_inputs doc
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
Pass CI
- vLLM version: v0.10.0
- vLLM main:
4be02a3776
---------
Signed-off-by: ChenTaoyu-SJTU <ctynb@qq.com>
1. Format the developer guide content to make it more clear
2. Add the patch doc for developer guide
Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>
