ci: add Crowdin sync for README navigation

Introduce an automated Crowdin synchronization flow for localized README navigation blocks. This adds a new GitHub Actions workflow (triggered on l10n README changes and manual runs) and a new script that maps locales to Crowdin languages, updates translations, and manages approvals for the README navigation string. It also refactors `validate-readme-navigation.mjs` to expose reusable helpers and a guarded `main()` entrypoint so the new sync script can reuse parsing and translation-generation logic.

Author: ReenigneArcher

.github/workflows/sync-readme-navigation-crowdin.yml

@@ -0,0 +1,37 @@
+---
+name: Sync README navigation to Crowdin
+permissions:
+  contents: read
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - l10n_master
+    paths:
+      - 'locale/**/README.md'
+
+concurrency:
+  group: crowdin-readme-navigation-sync
+  cancel-in-progress: false
+
+jobs:
+  sync:
+    if: github.repository_owner == 'LizardByte'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+
+      - name: Setup Node.js
+        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020  # v7.0.0
+        with:
+          node-version: 'latest'
+
+      - name: Install dependencies
+        run: npm ci --ignore-scripts
+
+      - name: Update and approve localized README navigation
+        run: npm run sync:readme-navigation-crowdin
+        env:
+          CROWDIN_TOKEN: ${{ secrets.CROWDIN_TOKEN }}