Add vite-plugin-thisone to helpers list

[SI-IC]

Adds vite-plugin-thisone to Framework-agnostic Plugins → Helpers.

Pick an element in the dev preview and copy its component path or a screenshot
to the clipboard, so an AI agent knows exactly which element you mean.
Works with Vue 3 and React, dev-only, stripped from production builds.

Checklist

• [x]Title as described.
  -[x] Make sure you put things in the right category.
• The description of your item should be a sentence with less than 24 words.
• Avoid using links and parentheses in description.
• Omit unnecessary words already provided in the context (e.g. for Vite, a Vite plugin).
• Use proper case for terms (e.g. GitHub, TypeScript, ESLint, etc.)
• [x]When mentioning tools, omit versions whenever possible (e.g. use TypeScript instead of TypeScript 4.x, but keep Vue 2 and Vue 3 as they're incompatible).
• When mentioning package names, use quotes whenever possible.
  -[x] Always add your items to the end of a list.

Plugins/Tools

• [] The plugin/tool is working with Vite 2.x and onward.
  Requires Vite 5 or newer
• The project is Open Source.
• The project follows the Vite Plugins Conventions.
• The plugin uses Vite-specific hooks and can't be implemented as a Compatible Rollup Plugin.
• The repo should be at least 30 days old.
• The documentation is in English.
• The project is active and maintained (inactive projects for longer 6 months will be removed without further notice).
• The project accepts contributions.
• Not a commercial product.