[CI] Add check for draft PRs (#5800)

* Add check for draft PRs

* Add necessary gitlab-ci boilerplate

* fix github API url (oops!)

* Add github action to retrigger pipeline

* fix workflow trigger

* rename trigger job

Co-authored-by: Benjamin Kampmann <ben@parity.io>

substrate/.github/workflows/trigger-review-pipeline.yml

@@ -0,0 +1,20 @@
+name: Trigger pipeline for review
+
+on:
+  pull_request:
+    types: [ready_for_review]
+
+jobs:
+  trigger:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Trigger pipeline
+        run: |
+          curl -X POST \
+            -F token="$TOKEN" \
+            -F ref="$REF" \
+            https://gitlab.parity.io/api/v4/projects/145/trigger/pipeline
+        env:
+          REF: ${{ github.event.number }}
+          TOKEN: ${{ secrets.GITLAB_TRIGGER_TOKEN }}