Add github action to publish static HTML doc

Add a workflow to generate and publish the project's documentation
on https://softwarefactory-project.github.io/sf-operator

(we will only know if it works after we merge this)

Change-Id: I2be623dc79f86a62e2b01885fe6e12e593654c28

.github/workflows/jekyll-gh-pages.yml

@@ -0,0 +1,45 @@
+name: Build static HTML documentation with Jekyll and GitHub pages
+
+on:
+  push:
+    branches: ["master"]
+
+  # Enable manual trigger
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Setup Pages
+        uses: actions/configure-pages@v3
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./doc/
+          destination: ./_site
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v2
+
+  # Deployment job
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v2