Run CI with Ruby 2.7 and 3.0 too

Author: st0012

.github/workflows/test.yml

@@ -8,6 +8,8 @@ permissions:  # added using https://github.com/step-security/secure-workflows
 jobs:
   ruby-versions:
     uses: ruby/actions/.github/workflows/ruby_versions.yml@master
+    with:
+      min_version: 2.7
 
   test:
     needs: ruby-versions