feat: sync mirror (#1260)

Author: 0marperez

.github/workflows/sync-mirror.yml

@@ -0,0 +1,20 @@
+name: Sync Mirror
+
+on:
+  push:
+    branches: [ main ]
+  workflow_dispatch:
+
+jobs:
+  git-sync:
+    # Only sync when pushing to source repo
+    if: github.repository == 'smithy-lang/smithy-kotlin'
+    runs-on: ubuntu-latest
+    steps:
+      - name: git-sync
+        uses: wei/git-sync@v3
+        with:
+          source_repo: "https://aws-sdk-kotlin-ci:${{ secrets.CI_USER_PAT }}@github.com/smithy-lang/smithy-kotlin.git"
+          source_branch: "main"
+          destination_repo: "https://aws-sdk-kotlin-ci:${{ secrets.CI_USER_PAT }}@github.com/smithy-lang/private-smithy-kotlin-staging.git"
+          destination_branch: "main"