docs: fix dial_timeout parameter documentation

[PrintNow]

Note: As English is not my native language, I used an LLM (Large Language Model) to help format and polish this PR description. The actual issue discovery and technical content are my own work.

1. What does this change do, exactly?

This change fixes the documentation for the dial_timeout parameter to correctly reflect its Go type and usage:

• Updates the parameter type from [integer] to [Duration] to match Go's time.Duration type
• Adds unit suffix 's' to the example value (30s)
• Updates the description to clarify that duration units are required
• Makes the default value notation consistent with Go duration format

2. Please link to the relevant issues.

Fixes #170

3. Which documentation changes (if any) need to be made because of this PR?

All changes in this PR are documentation changes in README.md. No additional documentation changes are needed.

4. Checklist

• I have written tests and verified that they fail without my change

  Not applicable as this is a documentation-only change

• I made pull request as minimal and simple as possible. If change is not small or additional dependencies are required, I opened an issue to propose and discuss the design first

  This is a minimal documentation fix that doesn't affect code or dependencies

• I have squashed any insignificant commits

  All changes are squashed into a single meaningful commit

• This change has comments for package types, values, functions, and non-obvious lines of code

  Not applicable as this is a documentation-only change

[mholt]

Thank you!