docs: add deploy preview (#15403)

.github/workflows/deploy-pr-preview.yml

@@ -0,0 +1,24 @@
+name: Deploy pr preview
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - closed
+    paths:
+      - "docs/sources/**"
+
+jobs:
+  deploy-pr-preview:
+    if: github.repository == 'grafana/loki'
+    uses: grafana/writers-toolkit/.github/workflows/deploy-preview.yml@main
+    with:
+      sha: ${{ github.event.pull_request.head.sha }}
+      branch: ${{ github.head_ref }}
+      event_number: ${{ github.event.number }}
+      title: ${{ github.event.pull_request.title }}
+      repo: loki
+      website_directory: content/docs/loki/latest
+      relative_prefix: /docs/loki/latest/
+      index_file: true