Add sync workflow with upstream

.github/workflows/sync.yml

@@ -0,0 +1,35 @@
+name: Sync with upstream
+
+on:
+  schedule:
+    - cron: '0 * * * *'
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout main branch of fork
+        uses: actions/checkout@v4
+        with:
+          ref: 'main'
+          fetch-depth: 0
+          token: ${{ secrets.REPO_SYNC_TOKEN }}
+
+      - name: Setup Git identity
+        run: |
+          git config user.name 'GitHub Actions'
+          git config user.email '[email protected]'
+
+      - name: Add remote upstream
+        run: git remote add upstream https://github.com/nesbox/TIC-80.git
+
+      - name: Fetch all history for all branches
+        run: |
+          git fetch --all
+
+      - name: Rebase changes
+        run: git rebase upstream/main
+
+      - name: Push changes
+        run: git push origin main --force-with-lease 
+