Show built doc links directly in PR GUI (#3711)

.github/workflows/show_link_to_built_docs.yml

+name: See built docs here!
+
+on:
+  status
+
+jobs:
+  circleci_artifacts_redirector_job:
+    runs-on: ubuntu-latest
+    name: Run CircleCI artifacts redirector
+    steps:
+      - name: GitHub Action step
+        uses: larsoner/circleci-artifacts-redirector-action@master
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          artifact-path: 0/docs/index.html
+          circleci-jobs: build_docs