Add workflow to export prelude translations

The workflow runs for pull requests that modify prelude.yaml, and
the export job runs if it's possible to modify the PR.

.github/workflows/export-translations.yml

@@ -0,0 +1,47 @@
+name: Export translations from prelude
+
+on:
+  pull_request:
+    paths: [prelude.yaml]
+
+jobs:
+  export:
+    runs-on: ubuntu-20.04
+
+    # Don't run this for the Weblate bot user as it already exports after import.
+    if: ${{ github.event.sender.id != 1607653 && github.event.pull_request.maintainer_can_modify == true }}
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.10'
+
+      - name: Install dependencies
+        run: |
+          python -m venv .venv
+          ./.venv/bin/activate
+          pip install -r requirements.txt
+
+      - name: Run the export translations script
+        run: python scripts/export-translations.py
+
+      - name: Create patch containing changes
+        run: git diff > sync-translations.patch
+
+      - name: Record pull request head data
+        run: |
+          echo 'export PR_HEAD_URL="${{ github.event.pull_request.head.repo.clone_url }}"' > git_vars.sh
+          echo 'export PR_HEAD_REF="${{ github.event.pull_request.head.ref }}"' >> git_vars.sh
+          echo 'export COMMIT_MESSAGE="Export translations from prelude"' >> git_vars.sh
+
+      - name: Upload data
+        uses: actions/upload-artifact@v4
+        with:
+          name: sync-translations-data
+          path: |
+            sync-translations.patch
+            git_vars.sh