feat: child menu support in navbar

[imfing]

• feat: implement child menu support in main navbar
• chore: update menu identifiers and add missing translations for development versions

In hugo.yaml define:

menu:
  main:
    - identifier: versions
      name: Versions
      weight: 2

    - identifier: development
      name: Development
      url: https://imfing.github.io/hextra/versions/latest/
      parent: versions
    - identifier: v0.9
      name: v0.9
      url: https://imfing.github.io/hextra/versions/v0.9/
      parent: versions

Replaces PR: #221

closes #224
closes #516

[netlify]

✅ Deploy Preview for hugo-hextra ready!

Name	Link
🔨 Latest commit	3419f45
🔍 Latest deploy log	https://app.netlify.com/projects/hugo-hextra/deploys/683c7ba7713bb90008e500ca
😎 Deploy Preview	https://deploy-preview-695--hugo-hextra.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[Copilot]

Pull Request Overview

This PR implements child menu support in the main navbar and updates related configurations. Key changes include adding a new navbar dropdown script, refactoring the navbar template to support dropdowns for items with children, and updating menu configuration and translations.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
layouts/partials/scripts/core.html	Enqueued the new navbar-dropdown.js script for handling dropdown logic.
layouts/partials/navbar.html	Added markup for dropdown menus on nav items with children.
exampleSite/i18n/zh-cn.yaml, ja.yaml, fa.yaml	Added translations for the new menu identifiers.
exampleSite/hugo_stats.json	Updated stats to include new CSS class references.
exampleSite/hugo.yaml	Updated menu configuration to include versions and child items.
assets/js/navbar-dropdown.js	Introduced a new JS module to manage dropdown behavior in the navbar.