Update how to work on documentation

[a2937]

Looking forward for reporting a security issue:
Please report security issues by following our security policy: https://contribute.freecodecamp.org/#/security

Describe the bug
Our documentation page will need to be updated at some point since we are using Starlight (powered by Astro) instead of Docsify.

Additional context
Most of it will need to be changed; including the sidebar and how things actually work.