ci: test against Ruby 4.0

Author: eitoball

.github/workflows/build.yml

@@ -5,12 +5,12 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.0', '3.1', '3.2', '3.3', '3.4']
+        ruby: ['3.0', '3.1', '3.2', '3.3', '3.4', '4.0']
         gemfile: ['active6.0.6', 'active6.1.7.6', 'active7.0.8', 'active7.1.3', 'rails6.0.6', 'rails6.1.7.6', 'rails7.0.8', 'rails7.1.3']
     runs-on: ubuntu-latest
     env:
       BUNDLE_GEMFILE: ${{ github.workspace }}/gemfiles/${{ matrix.gemfile }}.gemfile
-      BUNDLE_FORCE_RUBY_PLATFORM: ${{ matrix.ruby == '3.4' }}
+      BUNDLE_FORCE_RUBY_PLATFORM: ${{ matrix.ruby == '3.4' || matrix.ruby == '4.0' }}
       RUBY_OPT: --disable=did_you_mean
     services:
       mongodb: