Add a "How to Contribute" section for new contributors

[plainer-metes]

Overview

While the base/docs site offers useful content, it lacks a clear guide on how to contribute. A "How to Contribute" section would help first-time contributors understand how to make improvements and submit changes.
New contributors might not know how to propose edits, open issues, or add new content to the documentation. Without clear instructions, they may feel unsure about how to get involved or may incorrectly assume the contribution process.

Proposed Solution

Add a “How to Contribute” section to the documentation that explains the process for submitting changes, making suggestions, and adhering to any content standards.
The documentation contains an easy-to-understand guide for new contributors. The process for contributing should be simple and straightforward, allowing anyone to start contributing without confusion. No changes to the existing documentation content are needed.