Update color of search navbar and change pip command

[dianapaula19]

[Copilot]

Pull Request Overview

This PR aims to update the search navbar color by integrating a custom CSS file and update the pip installation command to fetch the latest release of the solt package.

• Added a setup function in conf.py to include custom.css for UI changes.
• Updated the pip command in BENCHMARK.md for installing the solt package.

Reviewed Changes

Copilot reviewed 2 out of 4 changed files in this pull request and generated no comments.

File	Description
doc/source/conf.py	Introduces a setup function to load custom.css, affecting search navbar styling
BENCHMARK.md	Updates the pip command to install the solt package from the new repository

Files not reviewed (2)

• doc/source/_static/custom.css: Language not supported
• doc/source/index.rst: Language not supported

[lext]

Looks good.