ci: Add workflow to automatically merge main into compat on tag push

.github/workflows/merge-main-into-compat.yml

@@ -0,0 +1,28 @@
+name: Merge Main Into Compat
+
+on:
+  push:
+    tags:
+      - v*
+
+jobs:
+  merge:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Configure git user
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+      - name: Merge main into compat
+        run: |
+          git fetch origin compat
+          git checkout compat
+          git merge --no-edit origin/main
+      - name: Push compat
+        run: |
+          git push origin compat