Added documentation on new dictionary value search config

[Nis-Knowit]

📋 Description

This PR adds documentation for the new dictionary value search feature introduced in umbraco/Umbraco-CMS#21200.

The feature allows searching dictionary items by their translation values in addition to keys. It's an opt-in configuration setting that's disabled by default to preserve backward compatibility and performance.

Changes:

• Added new configuration documentation: 17/umbraco-cms/reference/configuration/dictionarysettings.md
• Updated configuration index to include Dictionary Settings
• Documented the UseDictionaryValueSearch configuration option

📎 Related Issues (if applicable)

Related to code PR: umbraco/Umbraco-CMS#21200

✅ 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)

• Product: Umbraco CMS
• Version: 17

Deadline (if relevant)

Should be published along with the 17.2 RC due on 5th February.

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[sofietoft]

Thanks for the PR @Nis-Knowit ! 🙌
I'll tag this for pending release, so we can get it merged once the feature is added to the product.

[AndyButland]

There are a couple of small changes needed here as the code PR was worked on since this docs one was raised.

Please can you also update the "Deadline" in the PR description to say:

Should be published along with the 17.2 RC due on 5th February.

Thanks @Nis-Knowit.

[AndyButland]

Thanks for the updates @Nis-Knowit - looks fine to me now.