Add Azure Pipelines build status badge [ci skip]
copy from README.md. see r67146
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67152 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Add Azure Pipelines build status badge [ci skip]
copy from README.md. see r67146
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67152 b2dd03c8-39d4-4d8f-98ff-823fe69b080e