Add best practices on key management & not getting hacked

We should add this to Development Best Practices section specifically geared towards developers (avoiding malicious dependencies, accidentally committing your real keys, etc.

Start by locating the Development Best Practices section in this documentation repository and review its existing structure and guidance. Add developer-focused recommendations covering malicious dependencies and avoiding accidental commits of real keys, with the section complete and consistent with surrounding documentation.

Written by the indexing model from the issue text.