Docs: Fix typos, grammar, and formatting inconsistencies across documentation

[ekMartian]

Description

This PR fixes some documentation issues found across the repository, including typos, grammatical errors, and markdown formatting inconsistencies.

Changes

• ansi.css: Fixed a typo in the comment block ("deprecated an will" -> "deprecated and will").
• CONTRIBUTING.md:
  • Fixed grammar issues, like: ("ask as" -> "ask us").
  • Fixed C++ syntax typo in the example (std:string -> std::string).
• installation.md:
  • Removed accidental double-spacing in the wget command.
  • Fixed the Windows/WSL cmake command to use the correct Linux path syntax (. instead of .\).
• rebasing.md: Improved the grammar in the video explanation part.
• built-in functions.md: Standardized the header formatting (**Parameter** vs ****Parameter****) and fixed indentation alignment.
• design.md: Corrected grammar: ("no semantic is included" -> "no semantics are included").

Motivation

These changes improve the readability and professionalism of the documentation for new users and contributors.