Add trigger for internal gitlab CI

.github/workflows/diff.yml

@@ -0,0 +1,25 @@
+name: Diff
+on:
+  workflow_run:
+    workflows: ["PR Automation"]
+    branches: ["*"]
+    types:
+      - completed
+
+jobs:
+  render-diff:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Extract branch name
+        shell: bash
+        run: echo "branch=${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}" >> $GITHUB_OUTPUT
+        id: extract_branch
+
+      - name: Trigger diff on internal gitalb
+        run: |
+          curl -X POST \
+             --fail \
+             -F token=${{ secrets.GITLAB_CI_TOKEN }} \
+             -F ref=add/pipeline \
+             -F "variables[BRANCH]=${{ steps.extract_branch.outputs.branch }}" \
+             https://git.vshn.net/api/v4/projects/58084/trigger/pipeline