docs: quote pip extras install examples

[nyxst4ck]

Summary

• Quote pip install examples that include extras.

Why

• Shells such as zsh can expand unquoted bracket expressions before pip receives them.

Scope

• Files changed:
• README-zh.md
• README.md
• This does not change dependencies or runtime behavior.

Testing

• git diff --check

Maintainer Fit

• Small install-command correctness fix.
• Duplicate PR search terms checked: quote pip extras, quote optional dependency, zsh pip install extras, pip extras install examples

[SunnyHaze]

Thanks for the fix! The quoting is necessary for zsh, but single quotes are not portable to Windows cmd.exe. Could you please use double quotes instead?

uv pip install "open-dataflow[vllm]"

This should work across Bash, zsh, PowerShell, and cmd.exe.