Switch search backend from Lunr to Elasticsearch (#31257)

Co-authored-by: Peter Bengtsson <mail@peterbe.com>

.github/workflows/browser-test.yml

@@ -27,10 +27,26 @@ concurrency:
   group: '${{ github.workflow }} @ ${{ github.event.pull_request.head.label || github.head_ref || github.ref }}'
   cancel-in-progress: true
 
+env:
+  ELASTICSEARCH_URL: http://localhost:9200/
+
 jobs:
   build:
     runs-on: ${{ fromJSON('["ubuntu-latest", "ubuntu-20.04-xl"]')[github.repository == 'github/docs-internal'] }}
     steps:
+      - name: Install a local Elasticsearch for testing
+        # For the sake of saving time, only run this step if the test-group
+        # is one that will run tests against an Elasticsearch on localhost.
+        uses: getong/elasticsearch-action@95b501ab0c83dee0aac7c39b7cea3723bef14954
+        with:
+          # Make sure this matches production and `sync-search-pr.yml`
+          elasticsearch version: '7.11.1'
+          host port: 9200
+          container port: 9200
+          host node port: 9300
+          node port: 9300
+          discovery type: 'single-node'
+
       - name: Checkout
         uses: actions/checkout@dcd71f646680f2efd8db4afa5ad64fdcba30e748
         with:
@@ -62,5 +78,12 @@ jobs:
       - name: Run build script
         run: npm run build
 
+      - name: Index fixtures into the local Elasticsearch
+        run: npm run index-test-fixtures
+
+      - name: Check that Elasticsearch is accessible
+        run: |
+          curl --fail --retry-connrefused --retry 5 -I ${{ env.ELASTICSEARCH_URL }}
+
       - name: Run browser-test
         run: npm run browser-test