Docs: Add Oracle doc link to getting started page
Docs: Add Oracle doc link to getting started page

Since there is a recommended version of JDK, it would be helpful to provide a link to the Oracle documentation. Since there are many versions of Java, those that are new or infrequent users of Java would find the link helpful. Thanks!

Closes #11792

fubuki/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch