docs: add Chinese translation for generation_strategies.md

[liuyun7345]

What does this PR do?

This PR adds Chinese translation for the generation_strategies.md documentation.

Content translated

1. Basic decoding methods

   • Greedy search (贪婪搜索)
   • Sampling (采样)
   • Beam search (束搜索)

2. Custom generation methods

   • How to use custom generation methods
   • How to create custom generation methods
   • generate.py specifications
   • requirements.txt
   • README.md guidelines
   • Finding custom generation methods

Files changed

• docs/source/zh/generation_strategies.md - New Chinese translation file (325 lines)
• docs/source/zh/_toctree.yml - Added new document to table of contents

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline, Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the documentation guidelines.
• Did you write any new necessary tests?

Who can review?

@stevhliu (Documentation)

[stevhliu]

thanks for your translation!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.