Move to Jekyll publishing with GitHub Actions

Instead of using the built-in Jekyll-from-`gh-pages`-branch publishing, set up this workflow in GitHub Actions instead. This will allow extending the build with other preparations or installing custom plugins/different versions.

Author: QuLogic

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

@@ -0,0 +1,45 @@
+---
+name: Deploy Jekyll with GitHub Pages dependencies preinstalled
+
+on:
+  push:
+    branches: ["gh-pages"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Pages
+        uses: actions/configure-pages@v4
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./
+          destination: ./_site
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+
+  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@v4