Run CI with Ruby 3.0 too

Author: st0012

.github/workflows/test.yml

@@ -8,6 +8,9 @@ permissions:  # added using https://github.com/step-security/secure-workflows
 jobs:
   ruby-versions:
     uses: ruby/actions/.github/workflows/ruby_versions.yml@master
+    with:
+      # 2.7 breaks `test_parse_statements_nodoc_identifier_alias_method`
+      min_version: 3.0
 
   test:
     needs: ruby-versions