Better bundler caching for GitHub Actions (#750)

* Better caching for GitHub Actions

* Update `actions/checkout` to `v3`

.github/workflows/deploy.yml

@@ -15,23 +15,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
     - name: Setup Ruby
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: '3.0.2'
-    - name: Enable bundler cache
-      uses: actions/cache@v2
-      with:
-        path: vendor/bundle
-        key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-gems-
+        bundler-cache: true
     - name: Install deps
       run: |
-        gem install bundler
-        bundle config path vendor/bundle
-        bundle install --jobs 4 --retry 3
         npm install -g mermaid.cli
     - name: Setup deploy options
       id: setup