Fix grammar and clarity issues in CONTRIBUTING.md

[apravint]

This pull request improves the grammar, clarity, and overall readability of the CONTRIBUTING.md file. The changes include:

Corrected grammatical errors and awkward phrasing. Enhanced clarity and professionalism throughout the document. Ensured consistency in instructions and formatting. Updated steps and guidelines for contributors. These improvements make the contribution process easier to understand and more welcoming for new and existing contributors. No functional changes were made to the codebase.