fix: 🐛 Bundler cache for GitHub Actions (#47)

Specify Bundler version for GitHub Actions cache

Author: nikukyugamer

.github/workflows/config.yml

@@ -15,7 +15,9 @@ jobs:
         key: ${{ runner.os }}-gem-${{ hashFiles('**/Gemfile.lock') }}
         restore-keys: |
           ${{ runner.os }}-gem-
+    - name: Install appropriate version's Bundler
+      run: gem install bundler:1.17.3
     - name: $ bundle install
       run: |
         bundle config path vendor/bundle
-        bundle install --jobs=4 --retry=3
+        bundle _1.17.3_ install --jobs=4 --retry=3