text: Title: [Docs]  Improve DPSK docs in dark mode
  Body: ### Checklist
  
  - [x] 1. If the issue you raised is not a feature but a question, please raise a discussion at https://github.com/sgl-project/sglang/discussions/new/choose Otherwise, it will be closed.
  - [x] 2. Please use English, otherwise it will be closed.
  
  ### Motivation
  
  <img width="1393" alt="Image" src="https://github.com/user-attachments/assets/39d60ef8-c7fa-42e0-9961-5bd9c082209f" />
  
  I use html to write this docs and it looks bad. So could someone fix it here?
  
  https://github.com/sgl-project/sglang/blob/main/docs/references/deepseek.md
  
  ### Related resources
  
  _No response_