build: use tretuna/sync-branches to sync alpha with master (#2071)

* build: use tretuna/sync-branches to sync alpha with master

* build: use merge instead of squash on auto-merge

.github/workflows/sync-master-alpha.yml

@@ -0,0 +1,30 @@
+name: Sync alpha with master
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  sync-branches:
+    runs-on: ubuntu-latest
+    name: Syncing branches
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Set up Node
+        uses: actions/setup-node@v1
+        with:
+          node-version: 18
+      - name: Create Pull Request
+        id: cpr
+        uses: tretuna/sync-branches@1.4.0
+        with:
+          GITHUB_TOKEN: ${{ secrets.requirements_bot_github_token }}
+          FROM_BRANCH: master
+          TO_BRANCH: alpha
+      - name: Enable Pull Request Automerge
+        if: steps.cpr.outputs.pull-request-operation == 'created'
+        uses: peter-evans/enable-pull-request-automerge@v2
+        with:
+          token: ${{ secrets.requirements_bot_github_token }}
+          pull-request-number: ${{ steps.cpr.outputs.PULL_REQUEST_NUMBER }}