[fix] Node.js 16 actions are deprecated. Please update the following …

…actions to use Node.js 20: actions/checkout@v2, actions/cache@v2. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

.github/workflows/build-jekyll.yml

@@ -9,10 +9,10 @@ jobs:
   build_and_deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       # Use GitHub Actions' cache to cache dependencies on servers
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: vendor/bundle
           key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}