[FR] Add base pipeline to trigger react (#2768)

(cherry picked from commit c443aad)

.github/workflows/trigger-react.yml

@@ -0,0 +1,31 @@
+name: Trigger REACT Buildkite Pipeline
+
+on:
+  push:
+    branches: [ "main", "7.*", "8.*" ]
+    paths:
+      - 'rules/**/*.toml'
+  pull_request:
+    branches: [ "*" ]
+    paths:
+      - 'rules/**/*.toml'
+
+jobs:
+  trigger_buildkite:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Trigger a Buildkite REACT Build
+        run: |
+          curl -X POST "https://api.buildkite.com/v2/organizations/elastic/pipelines/react/builds" \
+            -H "Authorization: Bearer ${{ secrets.REACT_BUILDKITE_API_TOKEN }}" \
+            -H "Content-Type: application/json" \
+            -d '{
+              "commit": "HEAD",
+              "branch": "main",
+              "message": ":github: Triggered from a DR GitHub Action",
+              "env": {
+                "GITHUB_COMMIT_HASH": "${{ github.sha }}",
+                "GITHUB_HEAD_BRANCH": "${{ github.event_name == 'pull_request' && github.event.pull_request.head.ref || github.ref_name }}",
+                "GITHUB_SRC_BRANCH": "${{ github.event_name == 'pull_request' && github.event.pull_request.base.ref || github.ref_name }}"
+              }
+            }'