Add CI config file

.child1-ci.yml

+child1_job:
+  stage: test
+  tags: ["fml7qkaw"]
+  script:
+    - echo $TEST_VAR
+    - echo Done!

.gitlab-ci.yml

+child1_trigger:
+  trigger:
+    include: .child1-ci.yml
+    forward:
+      pipeline_variables: true
+
+downstream1_trigger:
+  trigger:
+    project: gitlab-qa-sandbox-group-6/group-for-variable-inheritance-fml7qkaw/downstream1-variable-inheritance-cd2bb6be9ac5dfd8
+    forward:
+      pipeline_variables: true