Add workflow to push the nvbench subtree to a remote repository.

.github/workflows/sync_nvbench.yml

@@ -0,0 +1,20 @@
+name: Sync nvbench
+
+on:
+  push:
+    branches:
+      #- main
+      - add_nvbench
+    paths:
+      - 'nvbench/**'
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+      - name: Push nvbench subtree
+        run: |
+          git subtree push --prefix nvbench [email protected]:alliepiper/nvbench.git subtree_test