ci: Job to auto-sync upstream changes

- Add a GitHub workflow for syncing upstream pasta_curves updates
- Set sync to occur every 15 minutes or on manual triggers
- on the dev branch, so as to not be rewritten automatically

.github/workflows/repo-sync.yml

@@ -0,0 +1,20 @@
+on:
+  schedule:
+  - cron:  "*/15 * * * *"
+  workflow_dispatch:
+
+jobs:
+  repo-sync:
+    name: Sync changes from upstream Nova
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        persist-credentials: false
+    - name: repo-sync
+      uses: repo-sync/github-sync@v2
+      with:
+        source_repo: "https://github.com/microsoft/nova.git"
+        source_branch: "main"
+        destination_branch: "main"
+        github_token: ${{ secrets.GITHUB_TOKEN }}