Add Content Security Policy check to built in health check list

[karl-sjogren]

📋 Description

Adds info about the CSP health check to the health check page.

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

The CSP check was added in 14.3, not sure how that works for the docs though.

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[eshanrnh]

Thanks for adding the CSP information to the PR, @karl-sjogren 🙌 The PR looks great.

I have added a suggestion to remove the repeated term and use the acronym after it is defined for the first time.