Clarify Dart getting started steps (#2062)
Clarify Dart getting started steps (#2062)

Based on feedback in https://github.com/dart-lang/dart-docker/issues/28
crate/docker-docs,Bonitasoft-Community/docker_docs,docker-solr/docs,infosiftr/docker-library-docs,infosiftr/docker-library-docs,docker-library/docs,docker-solr/docs,Bonitasoft-Community/docker_docs,nats-io/docker-docs,crate/docker-docs,Lightstreamer/docs,Lightstreamer/docs,nats-io/docker-docs,docker-library/docs,jetty-project/docker-docs,jetty-project/docker-docs