Add SerpApi to Supporters

[iluwatar]

Pull Request Template

What does this PR do?

Adds SerpApi to Supporters section of the README.md

[github-actions]

PR Summary

Adds SerpApi as a supporter in the README and introduces new banner assets for SerpApi. Includes updated Supporters section with logo, link and description; updates image selection for dark/light modes; adds gradient banner assets.

Changes

File	Summary
README.md	Introduces a new 'Supporters' section featuring SerpApi with a logo, description, and link; updates image selection for dark/light modes via color-aware banners; preserves existing sections.
assets/banner-wide-black.svg	New dark-mode supporter banner asset for SerpApi; added to be used in README supporters section.
assets/banner-wide-white.svg	New light-mode banner asset for SerpApi; added for color-mode support.
assets/banner-wide.svg	New gradient banner asset included for site-wide use and branding in README supporters visuals.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.69%. Comparing base (c842319) to head (2dd5840).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3591      +/-   ##
============================================
- Coverage     83.69%   83.69%   -0.01%     
+ Complexity     4257     4256       -1     
============================================
  Files          1115     1115              
  Lines         15066    15066              
  Branches        721      721              
============================================
- Hits          12610    12609       -1     
  Misses         2161     2161              
- Partials        295      296       +1     

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