add mirror-rolling-to-main.yaml. default branch is now rolling.

Signed-off-by: Tomoya.Fujita <[email protected]>

.github/workflows/mirror-rolling-to-main.yaml

@@ -0,0 +1,13 @@
+name: Mirror rolling to main
+
+on:
+  push:
+    branches: [ rolling ]
+
+jobs:
+  mirror-to-main:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: zofrex/mirror-branch@v1
+      with:
+        target-branch: main