chore(CI): Add upstream sync script

Author: potato4d

.github/workflows/sync.yaml

@@ -0,0 +1,33 @@
+name: todo
+
+on:
+  schedule:
+    - cron: 0 0 * * *
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [12.x]
+
+    steps:
+      - uses: actions/checkout@v1
+        with:
+          ref: master
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v1
+        if: steps.cache.outputs.cache-hit != 'true'
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Add upstream
+        run: |
+          git add remote upstream [email protected]:vuejs/docs-next.git
+      - name: Pull upstream changes
+        run: |
+          git add remote upstream [email protected]:vuejs/docs-next.git
+      - name: Sync it
+        run: |
+          git push origin master
+