Test Jekyll versions

.github/workflows/main.yml

@@ -3,7 +3,7 @@ name: CI
 on:
   push:
     branches:
-      - master
+      - test-jekyll
 
 concurrency:
   group: "pages"
@@ -12,6 +12,11 @@ concurrency:
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        jekyll: ["< 4.0", "< 5.0"]
+    env:
+      JEKYLL_VERSION: ${{ matrix.jekyll }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -88,16 +93,16 @@ jobs:
           css: true
           skip_git_check: true
 
-  deploy:
-    needs: [build, pa11y-ci, validate]
-    permissions:
-      pages: write
-      id-token: write
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Deploy to GitHub Pages
-        id: deployment
-        uses: actions/deploy-pages@v4
+  # deploy:
+  #   needs: [build, pa11y-ci, validate]
+  #   permissions:
+  #     pages: write
+  #     id-token: write
+  #   environment:
+  #     name: github-pages
+  #     url: ${{ steps.deployment.outputs.page_url }}
+  #   runs-on: ubuntu-latest
+  #   steps:
+  #     - name: Deploy to GitHub Pages
+  #       id: deployment
+  #       uses: actions/deploy-pages@v4

Gemfile

@@ -1,4 +1,5 @@
 source "https://rubygems.org"
 gemspec
 
+gem "jekyll", ENV["JEKYLL_VERSION"] if ENV["JEKYLL_VERSION"]
 gem "webrick"