Fix: Styling and Documentation Errors

[cypherpepe]

Description

This pull request addresses two issues:

1. Styling Fix in custom.css

   • Corrected the box-shadow property for the .wy-side-nav-search class to ensure proper CSS syntax by adding the missing px units. developer.mozilla.org

2. Documentation Typo Fix in contributing.rst

   • Corrected a typo: changed "requry" to "require" for improved clarity and correctness.

[github-actions]

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[mehtavishwa30]

Thanks for your contribution, @cypherpepe! Approving and merging now. :)