Update gitlab ci to trigger main website rebuild

.gitlab-ci.yml

@@ -4,6 +4,7 @@ stages:
   - build
   - test
   - publish
+  - trigger
 
 .docker-job-definition: &docker-job-template
   image: docker:stable
@@ -119,3 +120,9 @@ publish:docker-nightly:
   dependencies: []  # Do not pull any artifact
   only:
     - master
+
+trigger:child_pipelines:
+  stage: trigger
+  trigger:
+    project: infra/themes/kegtap-theme
+    branch: master