Feat (Insomnia): Raw template syntax UI option clarified

[TuannasCodeCatastrophe]

Description

Definition of done
Add information about the Raw template syntax option, maybe in an FAQ in the template tags docs.
It should be off by default but if it's enabled users won't be able to configure template tags with the form, they'll have to write it directly. In that case they won't get hints about what each value should be, so we may need reference docs about template tags arguments. TBD, not in the scope of this ticket.

Information
https://kongstrong.slack.com/archives/C044UFN49RT/p1756981092215769

Size
S

Fixes #2769

Preview Links

https://deploy-preview-3837--kongdeveloper.netlify.app/insomnia/template-tags/

Checklist

• Tested how-to docs. If not, note why here.
• All pages contain metadata.
• Any new docs link to existing docs.
• All autogenerated instructions render correctly (API, decK, Konnect, Kong Manager).
• Style guide (capitalized gateway entities, placeholder URLs) implemented correctly.
• Every page has a description entry in frontmatter.
• Add new pages to the product documentation index (if applicable).

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