Update Examine custom index examples

[AndyButland]

📋 Description

Updates the examples for how to configure and use a custom Examine index, both for Umbraco content and custom data.

📎 Related Issues (if applicable)

#7610

✅ 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)

Umbraco 16 and 17.

Deadline (if relevant)

Can be reviewed and published at any time.

[eshanrnh]

Looks great, @AndyButland 🙌 I have added a few suggestions to remove we/our, correct a typo, and format the UI components. I'll take care of those 💪