Update the example for line numbering and highlighting in the readme

[talatkuyuk]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything or linked relevant results below
• I made sure the docs are up to date
• I included tests (or that’s not needed)

Description of changes

I updated the example of line numbering and line highlighting in the readme due to the latest update in rehype-highlight-code-lines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (8fbc0eb) to head (cd06884).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #36   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          190       187    -3     
=========================================
- Hits           190       187    -3     

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[wooorm]

Thank you!