Add workflow for sync with upstream

.github/workflows/upstream_sync.yaml

@@ -0,0 +1,66 @@
+name: "Upstream Sync"
+
+on:
+  schedule:
+    - cron: "0 30 * * *"
+  workflow_dispatch:
+
+jobs:
+
+  sync:
+    name: Sync with upstream
+    runs-on: ubuntu-latest
+
+    outputs:
+      has_new_commits: ${{ steps.sync.outputs.has_new_commits }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          ref: sync/master
+
+      - name: Sync changes with upstream
+        id: sync
+        uses: aormsby/Fork-Sync-With-Upstream-action@v3.2
+        with:
+          target_sync_branch: sync/master
+          target_repo_token: ${{ secrets.GITHUB_TOKEN }}
+          upstream_sync_branch: master
+          upstream_sync_repo: alexta69/metube
+
+      - name: New commits found
+        if: steps.sync.outputs.has_new_commits == 'true'
+        run: echo "New commits were found to sync."
+
+      - name: No new commits found
+        if: steps.sync.outputs.has_new_commits == 'false'
+        run: echo "There were no new commits."
+
+  pr:
+    name: Create PR for upstream changes
+    runs-on: ubuntu-latest
+    needs: sync
+    if: needs.sync.outputs.has_new_commits == 'true'
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          ref: master
+
+      - name: Reset sync/master branch
+        run: |
+          git fetch origin sync/master:sync/master
+          git reset --hard sync/master
+
+      - name: Create pull request
+        uses: peter-evans/create-pull-request@v3
+        with:
+          branch: upstream-changes
+          title: "[sync] Changes from upstream"
+          body: |
+            Auto-generated by [create-pull-request](https://github.com/peter-evans/create-pull-request)
+          labels: |
+            automated
+          delete-branch: true