Add git-sync workflow to mirror repository

.github/workflows/git-sync.yml

+on: push
+jobs:
+  git-sync:
+    runs-on: ubuntu-latest
+    steps:
+      - name: git-sync
+        uses: wei/git-sync@v3
+        with:
+          source_repo: "lepus2589/LoadStaticSharedTargets"
+          source_branch: "refs/remotes/source/*:refs/tags/*"
+          destination_repo: "${{ secrets.MIRROR_DESTINATION_REPO_URL }}"
+          destination_branch: "refs/heads/*:refs/tags/*"
+          destination_ssh_private_key: ${{ secrets.DESTINATION_SSH_PRIVATE_KEY }}

.gitignore

 .*
 !.gitignore
 !.gitattributes
+!.github/
\ No newline at end of file