adding security section for items that don't fall under php security …

[tylercherpak]

…best practices

Description of the Change

Adding security section.

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests passed.

[tlovett1]

Overall looks good. Maybe mention the 10up Experience does many of these things out of the box?