feat: Add new GitLab mirroring GitHub Action

Author: bprusinowski

.github/workflows/gitlab-mirror-test.yml

@@ -0,0 +1,18 @@
+name: GitLab Mirror Test
+
+on: [push, delete]
+
+# Ensures that only one mirror task will run at a time.
+concurrency:
+  group: git-mirror
+
+jobs:
+  git-mirror:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: wearerequired/git-mirror-action@v1
+        env:
+          SSH_PRIVATE_KEY: ${{ secrets.GITLAB_SSH_PRIVATE_KEY }}
+        with:
+          source-repo: "git@github.com:visualize-admin/visualization-tool.git"
+          destination-repo: "git@gitlab.ldbar.ch:interactivethings/visualize-mirroring-test.git"